Mobile hybrid transmit/receive node for near-field wireless power delivery

ABSTRACT

A system and method for a mobile hybrid transmitter/receiver (TX/RX) node for wireless resonant power delivery is disclosed. A hybrid TX/RX can be configured to travel to remote, wirelessly-powerable receivers and deliver power to them wirelessly. A hybrid TX/RX device can include a transmitter component (TX), a receiver (RX) component, and a power store for storing power for supply to remote receivers. The TX/RX device can be configured in an autonomous unmanned vehicle operational to travel between a fixed source transmitter devices and one or more specified locations that may be host to one or more remote receivers. In the location of the one or more remote receivers, the TX component may function to wirelessly transfer power from the power store to the one or more remote receivers. In the location of the fixed source transmitter device, RX component can be configured to receive power via wireless power transfer, and to use the received power to at least partially replenish the power store.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a divisional of, and claims priority to, U.S.application Ser. No. 14/940,417, filed on Nov. 13, 2015, which is herebyincorporated in its entirety herein by reference.

BACKGROUND

Unless otherwise indicated herein, the materials described in thissection are not prior art to the claims in this application and are notadmitted to be prior art by inclusion in this section.

Electronic devices, such as mobile phones, laptops, and tablets, havebecome an integral part of daily life. Other machines, such as cars,which have conventionally used non-electric power sources, areincreasingly relying on electricity as a power source. As electronicdevices are often mobile, it may not be feasible for devices to stayconnected to a power source via wires. Thus, electronic devices may usebatteries to supply electric power when a device is not coupled to afixed power source.

Current battery technology, however, often does not meet the chargecapacity and/or discharge rate demands of electronic devices, which maylimit the range of moveable devices. Even in cases where batteries meetthe power demands of a given device, such a device usually must becoupled to a fixed charging source via wires in order to recharge itsbattery. Such wired charging mechanisms may limit the movement, and thusthe usability, of the device while it is being charged. Also, as thenumber of devices connected to a charging source increases, the numberof wires in the proximity of an electrical outlet may increase, causing“cord clutter.”

SUMMARY

In accordance with example embodiments, a system for resonant wirelesspower delivery can include a mobile node that is a hybridtransmitter/receiver (TX/RX) configured to travel to remote,wirelessly-powerable receivers and deliver power to them wirelessly. Ahybrid TX/RX device can include a transmitter component (TX), a receiver(RX) component, and a power store for storing power (e.g., a battery)for supply to remote receivers. The TX/RX device can be configured in anautonomous unmanned vehicle operational to travel between a fixed sourcetransmitter devices and one or more specified locations that may be hostto one or more remote receivers. In the location of the one or moreremote receivers, the TX component may function to wirelessly transferpower from the power store to the one or more remote receivers. In thelocation of the fixed source transmitter device, RX component can beconfigured to receive power via wireless power transfer, and to use thereceived power to at least partially replenish the power store.

Hence, in one aspect, an example embodiment presented herein provides amethod carried out by a mobile wireless power-delivery device (MWPD),wherein the MWPD comprises an autonomous mobile vehicle and a controllercommunicatively coupled to the autonomous mobile vehicle and configuredto carry out operations including causing the autonomous mobile vehicleto move the MWPD to specified geographic locations, the methodcomprising: (a) causing the MWPD to (i) move, by navigation of theautonomous mobile vehicle, to a first location in sufficient proximityto a remote receiver to cause the remote receiver to couple with a firstoscillating field generated by a transmit-resonator of a transmitter ofthe MWPD resonating at a first resonant frequency, wherein the firstoscillating field is at least one of an oscillating electric field or anoscillating magnetic field, and (ii) transfer power to the remotereceiver via the first oscillating field, wherein the transmit-resonatoris configured to couple power from a rechargeable power source of theMWPD into the first oscillating field; and (b) causing the MWPD to (i)move, by navigation of the autonomous mobile vehicle, to a secondlocation in sufficient proximity to a power-supply transmitter, otherthan the transmitter of the MWPD, to cause a receive-resonator of areceiver of the MWPD to couple with a second oscillating field generatedby the power-supply transmitter, wherein the second oscillating field isat least one of an oscillating electric field or an oscillating magneticfield, and (ii) receive power from the power-supply transmitter via thesecond oscillating field, wherein the receive-resonator is configured toresonate at a second resonant frequency in response to coupling to thesecond oscillating field, and wherein the receiver is configured to, inresponse to the receive-resonator resonating at the second resonantfrequency, transfer at least a portion of power of the secondoscillating field to the rechargeable component of the power source.

In another aspect, an example embodiment presented herein providesnon-transitory computer-readable medium having instructions storedthereon that, when executed by one or more processors of a mobilewireless power-delivery device (MWPD) comprising an autonomous mobilevehicle configured to move to specified geographic locations, cause theone or more processors to carry out operations including: (a) causingthe MWPD to (i) move, by navigation of the autonomous mobile vehicle, toa first location in sufficient proximity to a remote receiver to causethe remote receiver to couple with a first oscillating field generatedby a transmit-resonator of a transmitter of the MWPD resonating at afirst resonant frequency, wherein the first oscillating field is atleast one of an oscillating electric field or an oscillating magneticfield, and (ii) transfer power to the remote receiver via the firstoscillating field, wherein the transmit-resonator is configured tocouple power from a rechargeable power source of the MWPD into the firstoscillating field; and (b) causing the MWPD to (i) move, by navigationof the autonomous mobile vehicle, to a second location in sufficientproximity to a power-supply transmitter, other than the transmitter ofthe MWPD, to cause a receive-resonator of a receiver of the MWPD tocouple with a second oscillating field generated by the power-supplytransmitter, wherein the second oscillating field is at least one of anoscillating electric field or an oscillating magnetic field, and (ii)receive power from the power-supply transmitter via the secondoscillating field, wherein the receive-resonator is configured toresonate at a second resonant frequency in response to coupling to thesecond oscillating field, and wherein the receiver is configured to, inresponse to the receive-resonator resonating at the second resonantfrequency, transfer at least a portion of power of the secondoscillating field to the rechargeable component of the power source.

These as well as other aspects, advantages, and alternatives will becomeapparent to those of ordinary skill in the art by reading the followingdetailed description, with reference where appropriate to theaccompanying drawings. Further, it should be understood that thissummary and other descriptions and figures provided herein are intendedto illustrative embodiments by way of example only and, as such, thatnumerous variations are possible. For instance, structural elements andprocess steps can be rearranged, combined, distributed, eliminated, orotherwise changed, while remaining within the scope of the embodimentsas claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram illustrating the components of awireless power delivery system, according to an example embodiment.

FIG. 2 is a functional block diagram illustrating an impedance matchingcircuit coupled to a transmitter, according to an example embodiment.

FIG. 3 is a diagram illustrating a representation of a bidirectionalcoupler used in a mathematical derivation, according to an exampleembodiment.

FIGS. 4A to 4B illustrate a simplified circuit diagram of inductiveresonant coupling, according to an example embodiment.

FIGS. 5A to 5C illustrate a simplified circuit diagram of common modecapacitive resonant coupling, according to an example embodiment.

FIGS. 6A to 6B illustrate a simplified circuit diagram of differentialmode capacitive resonant coupling, according to an example embodiment.

FIG. 7 illustrates a method of delivering electrical power from atransmitter to one or more loads, according to an example embodiment.

FIG. 8 is a table illustrating modes of operation of a system, accordingto an example embodiment.

FIGS. 9A to 9B illustrate a TDMA wireless resonant coupling channel,according to an example embodiment.

FIG. 10 is a functional block diagram illustrating a wireless powerdelivery system employing side-channel communications, according to anexample embodiment.

FIG. 11 illustrates a method for confirming that a power transfer linkand a side-channel communication link are established with the samereceiver, according to an example embodiment.

FIG. 12 is a functional block diagram illustrating a wireless powerdelivery system employing multiplexed power transfer, according to anexample embodiment.

FIG. 13 illustrates a phase shift of a chain of repeaters repeating atransmitter near field, according to an example embodiment.

FIG. 14 illustrates a method of controlling the phase shift of nearfields in a system, according to an example embodiment.

FIG. 15 illustrates an implementation of a wireless power deliverysystem according to an example embodiment.

FIG. 16 is a flowchart illustrating a method of using a high-frequencytest pulse to determine one or more properties of reflecting entities ina near-field region of an oscillating field of a transmitter, accordingto an example embodiment.

FIGS. 17, 18, 19A, and 19B are simplified illustrations of unmannedaerial vehicles, according to example embodiments.

FIG. 20 illustrates a method of resonant wireless power transfer using amobile wireless power-delivery device, according to an exampleembodiment.

FIG. 21 is a simplified block diagram of a mobile power-delivery device,in accordance with an example embodiment.

DETAILED DESCRIPTION

Exemplary methods and systems are described herein. It should beunderstood that the word “exemplary” is used herein to mean “serving asan example, instance, or illustration.” Any embodiment or featuredescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other embodiments or features. Theexemplary embodiments described herein are not meant to be limiting. Itwill be readily understood that certain aspects of the disclosed systemsand methods can be arranged and combined in a wide variety of differentconfigurations, all of which are contemplated herein.

Furthermore, the particular arrangements shown in the Figures should notbe viewed as limiting. It should be understood that other embodimentsmay include more or less of each element shown in a given Figure.Further, some of the illustrated elements may be combined or omitted.Yet further, an exemplary embodiment may include elements that are notillustrated in the Figures.

Furthermore, the term “capacitor” as used herein should be understoodbroadly as any system, including one or more elements, with a capacitiveproperty. As such, the term “capacitor” may be used to refer to a lumpedcapacitive element and/or to a distributed capacitive element.Similarly, the term “inductor” as used herein should be understoodbroadly as any system, including one or more elements, with an inductiveproperty. As such, the term “inductor” may be used to refer to a lumpedinductive element and/or to a distributed inductive element.

I. Overview

Wireless power transfer involves the transmission of electrical powerfrom a power source to a receiver without coupling the receiver to thepower source with solid conductors (e.g., wires). Some conventionalwireless power delivery systems may include a transmitter and a receiverthat are inductively coupled via an oscillating magnetic field. Forinstance, a power signal from a power source may be delivered to atransmit-coil in a transmitter to create an oscillating magnetic field.This oscillating magnetic field passes through a receive-coil in areceiver and induces AC to flow in the receiver and to a load. Themagnitude of coupling between the transmitter and the receiver can berepresented by a coupling factor k, a dimensionless parameterrepresenting the fraction of flux coupling the transmitter and thereceiver. In order to establish efficient power transfer in suchconventional systems, the coupling factor k must be maintained at asufficiently high level. Accordingly, the receiver coil usually needs tobe located in close proximity to, and precisely positioned relative to,the transmitter coil. In addition, large transmitter and receiver coilsmay be necessary in order to ensure sufficient coupling and to achievereasonably efficient power transfer.

Systems, devices, and methods disclosed herein relate to wireless powerdelivery systems that utilize resonant coupling to transfer powerefficiently from a transmitter to a receiver. Such systems and methodsmay have less stringent proximity and/or positional requirements ascompared to conventional inductively-coupled wireless power systems.That is, systems and methods disclosed herein may provide efficientwireless power transfer even when the coupling factor k is small.Specifically, in accordance with example embodiments, power may betransferred between a resonantly-coupled transmitter and receiver via anoscillating field generated by the transmitter. The oscillating fieldmay include an oscillating magnetic field component and/or anoscillating electric field component.

In example systems, the transmitter may include a transmit-resonator andthe receiver may include a receive-resonator. A resonator, such as thetransmit-resonator or the receive-resonator can be characterized by oneor more resonant frequencies, among other factors. In particular, atransmit-resonator and a corresponding receive-resonator may beconfigured to resonate at a common resonant frequency. When resonating,the receive-resonator may produce an output signal oscillating at theresonant frequency. The output signal may then be rectified or otherwiseconverted to electrical power, which can be delivered to a load.

An oscillating electric and/or magnetic field may be described by itsresonant frequency, ω₀. Such fields have a resonant wavelength

${\lambda_{0} = \frac{2\pi\; c}{\omega_{0}}},$where c is the speed of light in the medium through which the field istransmitted. The region within approximately one resonant wavelengthfrom the resonator may be termed the “near field.” The electric and/ormagnetic field in the near field is predominantly non-radiative.Optionally, the near field may be considered the field that is at orbelow distances shorter than the 3*λ, where λ is a wavelength of thetransmitted signal. Further, a field strength of the near field decaysvery rapidly with distance. The region beyond approximately one or a fewresonant wavelengths from the resonator is known as the “far field.” Thefar field is almost exclusively radiative (e.g., RF radiation), and canbe described as the region beyond the 3*λ distance.

A resonator, such as the transmit-resonator and the receive-resonator,may be characterized in terms of an intrinsic loss rate Γ, which is ametric of energy dissipated over resonant cycles. The ratio

$Q = \frac{\omega_{0}}{2\Gamma}$defines a quality factor for the resonator expressed in terms of energyloss per cycle. A resonator that dissipates a smaller amount of energyper cycle generally has a higher quality factor Q. A system with a highquality factor Q (e.g., above 100) may be considered to be highlyresonant.

Resonant systems with high-Q resonators may be operable to transferpower with high efficiency, even in situations where there may be weakcoupling between the transmit-resonator and receive-resonator. That is,systems with a low coupling factor k (e.g., k=0.1) may still transferpower with high efficiency by employing resonators with sufficientlyhigh quality factor Q (e.g., Q>100), because the power transferefficiency is a function of the quality factor Q and the coupling factork. Accordingly, highly resonant systems may be operable to wirelesslytransfer power over a long range. Furthermore, in some embodiments,resonant systems may achieve greater efficiencies than systems employingwired power transfer.

As described above, to transfer power, transmit-resonators andreceive-resonators may be coupled via an oscillating magnetic fieldand/or an oscillating electric field. Accordingly, example embodimentsmay be operable using any one or more of three coupling modes at anygiven time: (i) inductive mode, (ii) differential capacitive mode, and(iii) common capacitive mode.

In inductive mode, at least one inductor of the transmit-resonatorreceives a signal from the power source and resonates to generate amagnetic field that oscillates at a resonant frequency ω₀. In such ascenario, at least one inductor of the receive-resonator may oscillatein response to being in proximity to the magnetic field. In differentialcapacitive mode, each capacitor of the transmit-resonator and thereceive-resonator develops capacitance between two conductors. In commoncapacitive mode, each capacitor of the transmit-resonator and thereceive-resonator develops a capacitance between a first conductor and aground or common conductor. In common capacitive mode, the ground orcommon conductor may include an earth connection. In other words, theground or common conductor may include an electrical connection to theearth's potential. The electrical connection may be a physicalconnection (e.g., using a metal stake), or may be a capacitiveconnection to the earth's potential. The transmitter may include acontroller to determine whether and when to deliver power via inductivemode, differential capacitive mode, and/or common capacitive mode and tocontrol various elements of the transmitter accordingly.

In resonant wireless power transfer, higher efficiencies may be achievedby dynamically adjusting impedances (resistance and/or reactance) on thetransmitting side and/or the receiving side. For instance, thetransmitter may include an impedance matching network coupled to thetransmit-resonator. The impedance matching network on the transmittingside may be controlled so as to continually or intermittently adjust theimpedance of the transmitter and associated elements. Similarly, thereceiver may include an impedance matching network coupled to thereceive-resonator. The impedance matching network on the receiving sidemay be controlled so as to continually or intermittently adjust theimpedance of the receiver and associated elements.

In an example embodiment, the controller may carry out operations tocreate a circuit model based on a transmit-receive circuit associatedwith the transmitter and the receiver. Using this transmit-receivecircuit, the coupling factor k can also be calculated. Because theimpedance associated with the receiver can be calculated from thereflected power received via the bidirectional RF coupler, the onlyremaining unknown in the circuit model is the coupling factor k for thetransmitter and the receiver. The circuit model determines a specificrelationship between the coupling factor k and the impedance of thereceiver. By determining the coupling coefficient k, an optimallyefficient condition for the power transfer may be calculated orotherwise determined. The impedance(s) on the transmitting and/orreceiving sides can be adjusted via the respective impedance matchingnetworks so as to achieve and/or maintain the optimally efficientcondition. In particular, dynamic impedance adjustment may be employedas the coupling between the transmit-resonator and the receive-resonatorchanges when the orientation and spatial relationship between thereceiver and the transmitter changes.

In some wireless power delivery systems described herein, thetransmitter may be operable to transfer power to any of a plurality ofreceivers. As many devices may be positioned within range of thetransmitter for wireless power transfer, the transmitter may beconfigured to distinguish legitimate receivers from illegitimate devicesthat are not intended recipients of power transfer. These illegitimatedevices may otherwise act as parasitic loads by receiving power from thetransmitter without permission. Thus, prior to transferring power to arespective receiver, the transmitter may carry out an authenticationprocess to authenticate the receiver. The authentication process may beconducted, at least in part, over a wireless side-channel communicationlink that establishes a secondary channel between the transmitter andthe receiver, separate from the resonant power link. Alternatively oradditionally, the transmitter may employ time-division and/orfrequency-division multiplexing to transfer power to a plurality oflegitimate receivers respectively.

In accordance with example embodiments, the resonant wireless powerdelivery system may include one or more resonant repeaters configured tospatially extend the near-field region of the oscillating field. Suchresonant repeaters may be passive, in the sense that they may be poweredonly by the near field in which they are positioned. A plurality ofrepeaters may be configured in a chain-like configuration (e.g., a“daisy-chain”), to extend the transmitter near field, such that eachsubsequent repeater in the chain resonantly repeats the near field of anearlier link in the resonant repeater chain. The spacing betweenrepeaters and/or between a transmitter and a repeater may be limited bydecay of the near field from one repeater to the next. Furthermore, amaximum distance to which the transmitter near field may be extended maybe limited due to an accumulated phase shift across chained repeaters.

In accordance with example embodiments, both the maximum repeaterspacing limitation and the accumulated phase shift limitations may beovercome by including additional capabilities in the repeaters. First,by using active repeaters that each include an independent power source,the active repeaters can “inject” additional power into the repeatedfields, and thereby mitigate decay of the near field that may otherwiseoccur. Second, cumulative phase delay across a chain or array ofrepeaters may be suppressed or eliminated by including one or more phaseadjustment elements in some or all of the repeaters. Additionally oralternatively, phase control may be introduced in repeaters by means ofmetamaterials. Furthermore, phase control of repeaters may beimplemented such that the transmitter and active repeaters behavetogether as a collective metamaterial.

In accordance with example embodiments, a wireless power delivery systemmay utilize test signals to probe physical properties of systemcomponents and/or wireless power transmission paths between systemcomponents. More particularly, a transmitter may include a signalgenerator, or the like, configured to transmit or broadcast one or moretypes of wireless signals across the region in which wireless powertransfer may occur. Such signals may be reflected by one or morereflecting entities (e.g., receivers, repeaters, etc.), and theirreflection may then be received by a test-signal receiver of thetransmitter. By analyzing phase and amplitude information of transmittedsignals and their reflections, the transmitter may thus determineelectrical properties of a reflecting entity, as well as of thetransmission path between the transmitter and the reflecting entity.Utilization of the test signal in such a manner may provide diagnosticcapabilities similar to that of a vector network analyzer (VNA), asapplied to a wireless power delivery system.

In an example system, test signals can span a broad frequency range toprovide a frequency sweep, in a manner like that of a VNA frequencysweep. Analysis of such a frequency sweep may then be performed todetermine an impedance of one or more receivers, a number of repeatersbetween the transmitter and a given receiver, a relative location of thetransmitter and the given receiver, and a characteristic impedance of awireless transmission path, among other properties of the system. Thisinformation can be used, in turn, to enhance the accuracy of powerdelivery, and to distinguish between legitimate receivers and possibleunauthorized receivers and/or parasitic devices. In other instances,test signals can be generated as pulses or chirps, being more narrowbandin frequency and or time. Analysis of reflections of such pulse signalsmay then be used in ranging applications, for example.

In some scenarios, a device may need wireless power-delivery while thedevice is out of range of a fixed resonant wireless power source. Insome cases, it may be impractical or difficult to provide a fixedtransmitter in a location where devices need to operate. Examplesinclude field devices, such as mobile delivery/transportation vehicles,remote communication equipment, and clusters of devices in remotelocations where fixed power sources are not available.

In accordance with example embodiments, a system for resonant wirelesspower delivery may include a mobile node or device that is a hybridtransmitter/receiver (TX/RX) configured to move, travel, and/or“commute” to remote receivers and deliver power wirelessly. In anexample system, a hybrid TX/RX device can include a transmittercomponent (TX) having functionality of a transmitter, a receiver (RX)component having functionality of a receiver, and a power store forstoring power (e.g., a battery) for supply to receivers. The power storemay also serve as a power supply for various functions of the hybridTX/RX device including, but not limited to, mobility (commuting),communications, control, and processing. The TX/RX device may take theform of an autonomous unmanned vehicle. In such a scenario, theautonomous unmanned vehicle may be operable to travel between a fixedtransmitters and one or more specified locations that may be host to oneor more remote receivers. In the location of the one or more remotereceivers, the TX component may be operable to wirelessly transfer powerfrom the power store to the one or more remote receivers. Whileproximate to the location of the fixed transmitter, the RX component maybe configured to receive power via wireless power transfer, and to usethe received power to at least partially replenish (e.g., refill and/orrecharge) its power store.

II. Example Systems and Operation

An example system 100 for wireless transfer of power is shown in FIG. 1.The system 100 may include various subsystems, elements, and componentsas described below. One or more subsystems may include a controllerconfigured to carry out one or more of a variety of operations. Inaccordance with example embodiments, a controller may include one ormore processors, memory, and machine language instructions stored in thememory that when executed by the one or more processors cause thecontroller to carry one or more of its controlling functions oroperations. A controller may also include one or more interfaces fordevice control, communications, etc.

In further accordance with example embodiments, various functions andoperations described below may be defined as methods that may be carriedwithin the system, where at least some aspects of the methods can beimplemented based on functions and/or operations carried out by one ormore controllers and/or one or more of processors. Other aspects of themethods may be carried out by other elements or components of thesystem, under control of one or another controller, in response toenvironmental factors, or in response to receiving or detecting asignal, for example.

In an example embodiment, a wireless power delivery system may include apower source configured to wirelessly deliver power to a load via atransmitter and a receiver. As shown in FIG. 1, system 100 may include atransmitter 102 and a receiver 108, both of which may be consideredsubsystems of system 100, and a controller 114. For the sake of brevityin FIG. 1 and elsewhere herein, control functions and operations aregenerally described as being carried out only by the controller 114.Thus, controller 114 may be viewed conceptually as a unified controlfunction. It should be understood, however, that as subsystems of system100, the transmitter 102 and receiver 108 may each include its owncontroller, as described elsewhere herein. Alternatively oradditionally, the controller 114 may include a distributed computingsystem, e.g., a mesh network.

As such, the various control functions and operations attributed tocontroller 114 may be implemented across one or more controllers, suchas ones included (but not shown) in transmitter 102 and receiver 108.For example, an operation described as being carried out by thetransmitter could be done so under control of a controller in thetransmitter. Similarly, an operation described as being carried out bythe receiver could be done so under control of a controller in thereceiver.

In addition to each of the transmitter 102 and receiver 108 possiblyincluding its own controller, each of them may also include and/beconstructed of various types of electrical components. For example,electrical components may include circuit elements such as inverters,varactors, amplifiers, rectifiers, transistors, switches, relays,capacitors, inductors, diodes, transmission lines, resonant cavities,and conductors. Furthermore, the electrical components may be arrangedin any viable electrical configuration, such as lumped or distributed.

Returning to FIG. 1, the transmitter 102 of system 100 may include atransmit-resonator 106. The transmit-resonator 106 may have a high Qvalue and may be configured to resonate at one or more resonantfrequencies. Transmitter 102 may be coupled with power source 104, whichmay be configured to supply transmit-resonator 106 with a signaloscillating at one of the transmit-resonator resonant frequencies. In anexample, the power source 104 may include a power oscillator to generatethe oscillating signal, which may be oscillating at one of thetransmit-resonator resonant frequencies. The power oscillator may bepowered by a power signal received from an electrical outlet. Forexample, the electrical outlet may supply the power source 104 with anAC voltage of 120 V at a frequency of 60 Hz. In other examples, thepower source may include a converter that may use a power from a powersignal, which may have a low-frequency (i.e. 60/50 Hz), to generate acarrier signal that has an oscillation frequency of one of thetransmit-resonant frequencies. The carrier signal may be modulated tocarry the power signal and may thus be the oscillating signal suppliedby the power source 104.

Furthermore, the resonant frequency ω₀ that the signal may oscillate at,also called the system resonant frequency, may be chosen by controller114 of system 100. Transmit-resonator 106 may resonate, upon receivingthe oscillating signal from source 104, and consequently, may generate afield oscillating at the system resonant frequency.

Receiver 108 may include a receive-resonator 112. The receive-resonator112 may have a high Q value and may also be configured to resonate atthe system resonant frequency. The receiver 108 may also include a load110. Thus, if receive-resonator 112 is in the range of the oscillatingfield (i.e. the field penetrates receive-resonator 112), resonator 112may wirelessly couple with the oscillating field, thereby resonantlycoupling with transmit-resonator 106. Receive-resonator 112, whileresonating, may generate a signal that may be delivered to the load 110.Note that in the implementation where the oscillating signal generatedby the power source 104 is a modulated carrier signal (generated by aconverter), the receiver 108 may include a filter network. The filternetwork may be used to isolate the power signal from the modulatedcarrier signal. The power signal (i.e. 50/60 Hz signal) may then bedelivered to the load 110.

In example systems, there may be more than one receiver. This isdescribed below in further detail.

Wireless power delivery systems may include at least one impedancematching network configured to increase the efficiency of wireless powertransfer. FIG. 2 illustrates an impedance matching network in a system,according to an exemplary embodiment. As illustrated in FIG. 2, theimpedance matching network 202 is coupled to the transmitter 204.Further, the impedance matching network 202 may be in series, parallel,or in any other configuration with the transmit-resonator 214. In someembodiments, an impedance matching network 218 may additionally and/oralternatively be coupled to the receiver. Furthermore, the impedancematching networks 202 and 218 may each include any combination of Lmatching networks, pi networks, T networks, and/or multi-sectionmatching networks.

In some embodiments, the system may deliver a determined power to theload by configuring an impedance matching network to match a determinedimpedance. Within examples, a controller of the system may determine apower to deliver from the transmitter to the load. The controller mayuse at least the reflected impedance, from the load to the transmitter,to determine the impedance that the impedance matching network(s) may beconfigured to match. Accordingly, the system may deliver the determinedpower to the load when the impedance matching network matches thedetermined impedance.

More specifically, the controller of the system may generate a model,such as a SPICE model, of the system to determine the impedance that theimpedance matching network may match. The model may include known valuessuch as the actual impedance of the load, which the controller mayreceive from the receiver using methods described herein. However, thecontroller may need to determine the actual power supplied to the loadfrom the transmitter and the reflected impedance, from the load to thetransmitter, in order to fully characterize the model of the system(e.g. to derive the coupling factor k). The controller may use the fullycharacterized model of the system to dynamically impedance match byprecisely determining the impedance that the impedance matching circuitmay match.

Therefore, the system may include a bidirectional coupler, which may beused to determine the actual power supplied to the load from thetransmitter and the reflected impedance from the load to thetransmitter. The bidirectional coupler may be used in conjunction with acomputer and/or a controller to precisely solve for an impedance of theload connected to it. The bidirectional coupler may also be used, inconjunction with a computer and/or a controller, to precisely solve forthe amount power leaving the power source. The value of the reflectedimpedance of a load and the amount power leaving the source may be usedto adjust the impedance matching network. Accordingly, the system may beconfigured to dynamically impedance match in a single step by using thebidirectional coupler to determine the actual power supplied by thesource and the reflected impedance from the load to the transmitter.

However, the value of the reflected impedance from the load may changedue to different factors, such as a change in the coupling between atransmitter and a receiver. The coupling between a transmitter and areceiver may change due to various factors, such as a change in thedistance between the transmitter and the receiver.

For example, the receiver may move during power transfer, which maychange the coupling between the transmitter and the receiver. Suchrelative movement may change the reflected impedance of the load.Accordingly, as the reflected impedance from the load to the transmitterchanges, the controller may be configured to continuously orintermittently solve for the actual power delivered to the load and thereflected load impedance, in order to dynamically impedance match.

FIG. 3 illustrates a network representation of a system, including thebidirectional coupler 302 that is coupled in cascade between a powersource 304 and a load 306, according to an exemplary embodiment. Asillustrated in FIG. 3, the bidirectional coupler may be coupled betweenthe power source at port 2 and the rest of the system (lumped into load306) at port 8. Generally, there may be forward and reflected powerwaves at each port of the bidirectional coupler (ports 1, 3, 4, and 5).

The forward and reflected waves, and thus the power and impedance, ateach port, may be precisely determined by fully characterizing the RFproperties of the bidirectional coupler. For instance, a mathematicalrelationship between the incoming and outgoing waves on each of thebidirectional coupler 302's ports may be used to precisely calculate thepower delivered to the load 306 and the load 306's reflected impedanceback to the source 304. The mathematical relationship may use anS-parameter characterization of the bidirectional coupler 302 to relatebetween the incoming and outgoing waves on each of the bidirectionalcoupler 302's ports.

The bidirectional coupler 302 may operate by coupling forward power fromport 1 to port 3. An attenuated forward power may be coupled to port 4and sampled at measurement FWD port 6. Additionally, a small amount offorward power may also be coupled into port 5 and measured at REF port7.

Likewise, reflected power is coupled from port 3 to port 1, and anattenuated power may be coupled to port 5 and sampled at measurement REFport 7. Additionally, a small amount of reflected power may be coupledinto port 4 and measured at FWD port 6. Despite these non-idealities, ofthe forward power coupling to port 5 and the reflected power coupling toport 4, a computer and/or a controller may precisely calculate the powerdelivered to the load 306 and the load 306's reflected impedance.

The premeasured values of the mathematical relationship (A) may includethe 4×4 S-parameter matrix and the input reflection coefficient, anS-parameter, of power source 302. Further, the non-idealities in theoperation of the bidirectional coupler may be accounted for bypremeasuring the 4×4 S-parameter matrix of the bidirectional coupler302. In some embodiments, the S-parameters may be premeasured using avector network analyzer (VNA). The measured S-parameters may be storedin a lookup table that a controller of system 300 may have access to.Similarly, a premeasured impedance of source 304 may be used tocalculate S₁₁. The calculated value may also be stored in the samelookup table that the S-parameters of bidirectional coupler 302 werestored in.

Further, as explained above, bidirectional coupler 302 may be used toperiodically make real-time measurements of waves that may be used tosolve for the power delivered to the load 306 and the load 306'sreflected impedance. Specifically, in order to precisely calculate thepower delivered to the load 306 and the load 306's reflected impedance,both the absolute magnitude of the power signals at ports 6 and 7 may bemeasured along with the phase of each signal with respect to the other.FWD and REF may include any measurement device or circuitry capable ofmeasuring signals, e.g., an ammeter, a voltmeter, a spectrum analyzer,etc. Furthermore, FWD and REF may send information indicative of therespective measured signals to the controller of the system.

Furthermore, certain configurations of network 300 may simplify theS-parameter characterization of the bidirectional coupler 302. Bydesign, FWD 308 and REF 310 may be impedance matched to the transmissionline that carries the signals to each port to prevent signals fromreflecting when measured at each port. For example, FWD port 308 and REFport 310 may be 50Ω terminated when a transmission line that hascharacteristic impedance (Z₀) of 50Ω is used to carry the signal to eachport.

Accordingly, a controller of a wireless power delivery system may use abidirectional coupler to solve for the reflected impedance of the loadand the power delivered to the load. The system may use the solved forvalues in the model of the system to fully characterize the system. Assuch, at least the coupling factor k may be calculated. Further, thecontroller may use the model of the system to predict the amount ofpower that may be delivered to a load by adjusting the impedance thatthe impedance matching circuit may match.

Further, the controller may periodically measure the reflected impedanceof the load and the power delivered to the load, according to apredetermined time period, which may range from microseconds to tens ofseconds in length. After each measurement, the controller mayperiodically adjust at least one impedance matching network of thesystem. In an example, a controller may measure the reflected impedanceand may accordingly adjust an impedance matching network everymillisecond using the method described above. Other time intervals arepossible. Alternatively, the controller may measure the reflectedimpedance of the load and the power delivered to the load continuously.In such a scenario, the controller may continuously adjust an impedancematching network of the system to deliver a determined power to theload.

In some embodiments, the wireless power delivery system may include aplurality of receivers coupled to a single transmitter with a singlebidirectional coupler. In such a scenario, each receiver may reflect asignal to the transmitter due to a possible impedance mismatch at eachload coupled to each receiver. The controller may use the measuredvalues to fully characterize the system in order to determine animpedance that the impedance matching network may match.

In some embodiments, a plurality of receivers may be coupled to a singlebidirectional coupler. The bidirectional coupler may use time-divisionmultiplexing (TDM) to send the reflected signal of each receiver to themeasurement device during a given interval of time. The controller maythen use the method described above to solve for the reflected impedanceof each load coupled to each respective receiver.

The controller of the system may adjust at least one impedance matchingcircuit based on the measured values. In an example embodiment, a systemwith a plurality of receivers may include an impedance matching networkcoupled to the transmitter and/or to each of the receivers. However, asthe transmitter may receive different reflected impedances from eachload, it may not be possible for the controller to adjust the impedancematching network to simultaneously match the reflected impedance of eachreceiver and the impedance of the power source. Accordingly, in someembodiments, the controller may adjust at least one impedance matchingnetwork of the impedance matching networks coupled to each of thereceivers. In other embodiments, the controller may adjust the impedancematching network, coupled to the transmitter, to match the reflectedimpedance of a selected receiver from the plurality of receivers. Assuch, the selected receiver, whose reflected impedance was matched atthe impedance matching network, may proportionately receive more powerthan the other receivers in the system. In some embodiments, wirelesspower delivery to the selected receiver may be more efficient than suchpower delivery to other receivers of the plurality of receivers.

In other examples, a system with a plurality of receivers may performimpedance matching according to time-division (TDM) and/orfrequency-division (FDM) multiplexing. For instance, in a TDM scheme,each receiver may be configured to couple to the transmitter with asingle impedance matching network during a specific time interval. Thesystem may receive a reflected signal from a receiver during thespecific time interval that the receiver is coupled to the transmitter.In such a scenario, the controller may adjust the impedance matchingnetwork such that each receiver may receive maximum power during theinterval that the receiver is coupled to the transmitter. In an exampleembodiment, each receiver of the plurality of receivers may be assigneda respective time slot according to a receiver priority or a receiverorder. The time slots may be equal in duration, but need not be equal.For example, receivers with higher receiver priority may be assigned tolonger time slots than those receivers with a lower receiver priority.

In a FDM scheme, each receiver may be configured to couple to thetransmitter with on a specific respective frequency. The system mayreceive a respective reflected signal from each receiver on the specificfrequency that the receiver is coupled to the transmitter on. In such ascenario, the controller may adjust the impedance matching network(s),which may be connected to the transmitter and/or to each of thereceivers, such that each receiver may receive a determined amount ofpower.

In yet another example of a system with a plurality of receivers, acontroller may determine the power that each receiver may receivesimultaneously from the transmitter by adjusting the impedance matchingnetwork. Specifically, the impedance of the impedance matching networkmay determine, at least in part, the amount of power that each receivermay receive. For example, each receiver may receive power based on atleast a difference between the receiver's impedance and that of theimpedance matching network. Accordingly, the controller may adjust theimpedance matching network so as to increase or decrease an amount ofpower delivered to a respective receiver, based at least on thereceiver's impedance.

A controller may determine the amount of power that each receiver mayreceive from the transmitter based on various parameters. In an exampleembodiment, each receiver may be associated with a respective prioritysuch that higher priority receivers may receive more power during asingle power distribution cycle than lower priority receivers. In otherexamples, a current charging state of the receiver (if the receiver iscoupled to a load that includes a battery), may determine the amount ofpower that a receiver may receive. That is, a receiver with a lowbattery level may receive higher priority than a receiver with a fullbattery. It is understood that the controller may distribute power toeach receiver of the plurality of receivers based on a variety of otherparameters.

Within examples, a controller may receive information indicative of atleast one parameter from a receiver when authenticating the receiver. Assuch, the controller may generate a dynamic priority list based on thereceived information. In an example embodiment, the dynamic prioritylist may be updated when a receiver connects or disconnects from atransmitter. Further, a controller may store the received informationand the corresponding dynamic priority lists either locally or on aserver. In other examples, a receiver may send a controller updatedinformation if a parameter of the receiver changes after the initialsynchronization process. In other examples, a controller mayperiodically query a receiver, via a side-channel communication link,for example, to request information regarding the state of the receiver.As such, the controller may receive, via the side channel, for example,information such as the current charging state of a battery of areceiver or the current power requirements of a receiver.

In yet other examples, a system may include one or more impedancematching networks in each receiver of the plurality of receivers. Asystem may additionally or alternatively include impedance matchingnetworks in the transmitter and at least one of the receivers. In suchscenarios, a controller may be configured to adjust a plurality ofimpedance matching networks of the system such that each receiver mayreceive a determined amount of power from the transmitter.

Additionally or alternatively, the system may use the dynamic impedancematching method described above to detect a parasitic receiver.Specifically, a controller of the system may use information, such as anominal impedance, about authorized receivers to generate a circuitmodel of at least a portion of the wireless power delivery system.Additionally or alternatively, the controller may generate the circuitmodel based on an approximation, estimation, or other determination of acoupling condition between the transmitter and the receiver, which maybe based on their relative locations. Based on the circuit model, thecontroller may calculate an ideal power reception amount that it mayreceive from each receiver. Accordingly, the controller may compare thecalculated ideal power received and the actual power received. If theideal and actual power received are not equal within a specified marginof error, the controller may determine that a parasitic device may bepresent in the system. For example, the controller may determine that aparasitic device may be present in the system if the value of thecalculated power received varies by more than 10% of the value of theactual power received. Additionally or alternatively, the controller mayuse other methods disclosed herein to identify parasitic receivers.

A. Coupling Modes

A transmitter and a receiver of a wireless power delivery system mayestablish a wireless coupling resonant link, and thus become resonantlycoupled, via various coupling modes. Each coupling mode is associatedwith a type of resonator that may be included in a transmitter and/or areceiver. Accordingly, a system may excite a type of resonator so as toprovide a wireless resonant link via the associated coupling mode.Furthermore, the system may maintain multiple wireless resonant links ofdifferent coupling mode types at any given time. Within examples, atransmitter and a receiver of a system may include at least one of threeresonator types. As such, the operational state of a system may utilizeat least one of three resonant coupling modes.

FIG. 4A and FIG. 4B illustrate an inductive resonant coupling mode, thefirst coupling mode, according to an exemplary embodiment. Each oftransmit-resonator 402 and receive-resonator 404 may include at least aninductor. Further, each resonator may be configured to resonate at leastat the system resonant frequency of system 400. Transmit-resonator 402may resonate upon receiving a signal, from power source 406, that isoscillating at the system resonant frequency. Thus, transmit inductor408 of transmit-resonator 402 may generate a magnetic field oscillatingat the system resonant frequency. Receive-resonator 404 may couple withthe oscillating magnetic field if it is within proximity to thetransmit-resonator 402. As a result, a wireless coupling resonant linkmay be established. Coupled receive-resonator 404 may then resonate, andmay therefore generate a signal that may be delivered to load 412.

Additionally or alternatively, the system may include a transmitterand/or a receiver that include a capacitive resonator, which may beoperable to couple the transmitter and the receiver. In an exampleembodiment, each of the transmitter capacitive resonator and thereceiver capacitive resonator may include at least a capacitor. Thetransmit-resonator may resonate upon receiving, from the power source, asignal oscillating at the system resonant frequency. As thetransmit-resonator resonates, the capacitor of the transmit-resonatormay generate an electric field oscillating at the system resonantfrequency. The receive-resonator, if in proximity to thetransmit-resonator, may couple with the oscillating electric field;thereby establishing a wireless coupling link between the transmitterand the receiver. As such, the receive-resonator may resonate, and maytherefore generate a signal that may be delivered to a load coupled tothe receiver.

In an example embodiment, a system may include at least one of two typesof capacitive resonators, each of which may be associated with arespective coupling mode. The two capacitive resonators differ in theconfiguration of their respective capacitors. The first capacitiveresonator may include a common mode capacitor, which may support acapacitance between a single conductor and ground. A common modecapacitive resonator may be operable to provide a wireless coupling linkvia a coupling mode termed common mode. The second capacitive resonatortype may include a differential mode capacitor, which may support acapacitance between two conductors. A differential mode capacitiveresonator may be operable to provide a wireless coupling link via acoupling mode termed differential mode.

FIG. 5A, FIG. 5B, and FIG. 5C illustrate a system, in threerepresentations, that includes a common mode capacitive resonator,according to an exemplary embodiment. Each of transmit-resonator 502 andreceive-resonator 504 includes a common mode capacitive resonator. Assuch, each resonator includes a common mode capacitor that includes aconductor and ground reference 506. Ground reference 506 may conductcurrent to complete the circuit of transmitter 508 and receiver 510.Further, transmitter 508 may be coupled with power source 512 that maybe connected on one end to ground reference 506 and on the other end toat least transmitter conductor 514. Optionally power source 512 need notbe connected to the ground reference 506. Transmit-resonator 502 mayresonate upon receiving, from power source 512, a signal that isoscillating at the system resonant frequency. As the transmit-resonator502 resonates, common mode capacitor 516 of the transmit-resonator 502may generate an electric field oscillating at the system resonantfrequency. Receiver 510 may include load 518 that may be connected onone end to ground reference 506 and on the other end to receiverconductor 520. If within the near field of transmit-resonator 502, thereceive-resonator 504 (which includes common mode capacitor 522) maycouple with the oscillating electric field, thereby establishing awireless resonant coupling link. As such, receive-resonator 504 mayresonate, and may generate a signal that may be delivered to the load.FIG. 5B illustrates the circuit diagram of a system using common modewhere there is a conductive path through ground, as explained above.FIG. 5C illustrates the circuit diagram of a system using common modewhere there is a capacitive connection to ground, as explained above.

In some embodiments, the ground reference of the common mode capacitorsmay be connected to earth ground via a direct or an indirect connection.For example, the ground reference may include the infrastructure of abuilding housing the wireless power system, which may include anindirect connection to earth ground. In other examples, the groundreference may include a conductive object connected to common modecapacitors. As such, the conductive object may provide a conductivereturn path in a circuit including a transmitter and/or a receiver.

FIGS. 6A and 6B illustrate a system 600, in two representations, thatincludes a differential mode capacitor, according to an exemplaryembodiment. Each of transmit-resonator 602 and receive-resonator 604 mayinclude at least one capacitor. Power source 606 may supply a signaloscillating at a system resonance frequency to transmit-resonator 602.Transmit-resonator 602 may resonate upon receiving the signal fromsource 606. As transmit-resonator 602 resonates, transmitterdifferential mode capacitor 608 may generate an electric fieldoscillating at the system resonant frequency. Receive-resonator 604, ifin proximity to the transmit-resonator 602, may couple with theoscillating electric field. As such, a wireless resonant coupling linkmay be established between the transmitter and the receiver.Furthermore, receiver differential mode capacitor 610 may resonate, andmay therefore generate a signal that may be delivered to load 612coupled to receiver 614.

In example embodiments, a system may establish a wireless resonantcoupling link between a transmitter and a receiver according to one ormore coupling modes that include a capacitive resonant coupling mode andan inductive resonant coupling mode. A transmitter and a receiver mayeach include the resonators necessary to establish a wireless link ineach of the coupling modes. Furthermore, a wireless coupling link may bemaintained between the transmitter and the receiver that utilizesdifferent coupling modes simultaneously or individually. In someexamples, the resonators may include a single circuit element that maybe configured to operate either as an inductor, a capacitor, or both. Inan example, an element may include coils shaped like a pair of conductorplates, such that the element may operate as an inductor and/or acapacitor. In other examples, a transmitter or receiver may includemultiple resonators arranged in a resonator bank. The resonator bank mayinclude at least one resonator that may include an inductor, and atleast one resonator that may include a capacitor. Accordingly, theresonator bank may be configured to establish wireless resonant couplinglinks in capacitive and inductive resonant coupling modes.

FIG. 7 illustrates a flowchart showing a method 700 that may establish awireless resonant coupling link between a transmitter and a receiver ofa system, according to an exemplary embodiment. In some embodiments,method 700 may be carried out by a controller of a system.

Furthermore, as noted above, the functionality described in connectionwith the flowcharts described herein can be implemented asspecial-function and/or configured general-function hardware modules,portions of program code executed by one or more processors forachieving specific logical functions, determinations, and/or stepsdescribed in connection with the flowchart shown in FIG. 7. For examplethe one or more processors may be part of controller 114. Where used,program code can be stored on any type of non-transitorycomputer-readable medium, for example, such as a storage deviceincluding a disk or hard drive.

In addition, each block of the flowchart shown in FIG. 7 may representcircuitry that is wired to perform the specific logical functions in theprocess. Unless specifically indicated, functions in the flowchart shownin FIG. 7 may be executed out of order from that shown or discussed,including substantially concurrent execution of separately describedfunctions, or even in reverse order in some examples, depending on thefunctionality involved, so long as the overall functionality of thedescribed method is maintained.

As shown by block 702, of FIG. 7, method 700 may involve determining anoperational state of a system. The determined operational state mayinclude at least one coupling mode. For example, the determinedoperational state may include any of the wireless coupling modesdescribed herein. Within examples, the determined operational state maybe determined by a controller of the system. As shown by block 704,method 700 further includes causing a power source that is coupled to atransmitter of a system to provide a signal at an oscillation frequency.For example, the oscillation frequency may be one of the one or moreresonant frequencies of the transmitter. In some embodiments, theoscillation frequency may be a frequency within a range of resonantfrequencies of the transmit-resonator.

Accordingly, as shown by block 706, a transmit-resonator may resonate atthe oscillation frequency upon receiving the signal from the powersource of the system. The oscillating transmit-resonator may generate afield oscillating at the oscillation frequency. In some embodiments, thetransmit-resonator may generate a field that may be oscillating at afrequency within a range of resonant frequencies of thereceive-resonator. As shown by block 708, if a receive-resonator islocated within the range of the oscillating field generated by thetransmit-resonator, the receive-resonator may also resonate at theoscillation frequency. As a result, as shown by block 710, a wirelessresonant coupling link may be established according to the determinedoperational state. Finally, method 700 may cause the transmitter todeliver electrical power to each of the one or more loads via theestablished wireless resonant coupling link, as shown by block 712.

FIG. 8 illustrates different combinations of coupling modes that mayform wireless resonant coupling link, according to an exemplaryembodiment. In an example embodiment, a system may include a transmitterand a receiver both having three different types of resonator elements(e.g. an inductor, a common-mode capacitor, and a differential-modecapacitor). Accordingly, a wireless resonant coupling link between thetransmitter and the receiver may include various combinations of thethree different coupling modes. Accordingly, combinations 1-7 eachinclude supporting a wireless resonant coupling link via at least onecoupling mode. Operational state 8 represents when the system is notoperating or when the transmitter and receiver are not coupled via awireless resonant coupling link. Within examples, the variouscombinations of coupling modes forming the wireless coupling linkbetween the transmitter and the receiver may be determined andcontrolled by a controller. In other examples, a user may provide aninput to the controller that may direct the system to form a wirelessresonant coupling link with a given combination of coupling modes.

In an example embodiment, a system may establish wireless resonantcoupling links between a transmitter and a plurality of receivers. Insuch a scenario, the plurality of receivers may all operate in a singleoperational state to establish simultaneous links to the transmitter. Inother scenarios, each of the receivers may establish a wireless resonantcoupling link with the transmitter using a different coupling mode.Transmitters of such systems may include a resonator bank configured toenable simultaneous links with a plurality of receivers via one or morecoupling modes.

As explained elsewhere herein, a system may employ time divisionmultiple access (TDMA) to establish a wireless resonant coupling linkthat may be shared by a plurality of receivers. Specifically, thewireless resonant coupling link may be divided into different time slotswithin a given time frame. As such, each receiver of the plurality ofreceivers may receive electrical power from the transmitter during anassigned time slot within the given time frame. In other words, withinthe given time frame, the transmitter may distribute power to a givenreceiver during a given time slot. Each receiver may be assigned toreceive power during one or more time slots within the time frame.

FIG. 9A illustrates a TDMA wireless resonant coupling link, according toan exemplary embodiment. Specifically, the ten time slots (T1-T10) mayrepresent a single time frame of power distribution. The samedistribution may be repeated in subsequent time slots T11-T20 and/ortime frames (not shown). Furthermore, a controller of the system mayassign each receiver of the system one or more time slots during whichthe receiver may receive power from the transmitter. In this example,receivers 1-4 are configured to receive power from the transmitterduring various time slots of this time frame, whereas receiver 5 is notconfigured to receive power. In such a scenario, a controller may assignreceivers 1-4 specific time slots during which they may receive powerfrom the transmitter. The power may be transferred to a receiver duringa given time slot according to any of the modes of operation of asystem. Within examples, the controller may determine the operationalstate (e.g., the coupling mode type(s)) of each receiver during eachinterval of time. In other examples, the operational state may be inputby a user of the respective receiver.

FIG. 9B illustrates a TDMA wireless resonant coupling link, according toan exemplary embodiment. Similar to the system illustrated in FIG. 9A,the ten time slots (T1-T10) may represent a single frame of powerdistribution. However, as illustrated in FIG. 9B, more than one receivermay receive power simultaneously from the transmitter. Furthermore, eachreceiver may receive power according to an of the modes of operation ofthe system. In some examples, the receivers receiving powersimultaneously may receive power according to the same mode ofoperation. In other examples, the receivers receiving powersimultaneously may receive power according to different modes ofoperation.

In accordance with some embodiments, the components (e.g., transmitterand receiver) of a system may include circuit elements (shown as element212 in FIG. 2, element 414 in FIG. 4, element 524 in FIG. 5, and element616 in FIG. 6), such as inductors, capacitors, transistors, inverters,amplifiers, rectifiers, varactors, relays, diodes, transmission lines,resonant cavities and switches, which may be arranged to facilitateswitching between the different coupling modes of a system. For example,a system may switch between the different modes by having both a coiland one or two (or more) conductors in a combination of series-parallelconnections. In other examples, a system may dynamically suppress orenhance a coupling mode by dynamically adding lumped element reactivecomponents in series or parallel between the elements of the resonatorof each mode.

In some examples, the operational state of a system may be determined bya controller of the system. For example, a controller may determine themode of the operation of the system based on data that it may receivefrom a receiver, such as the receiver's power demands, preferredoperational state, and location. Alternatively or additionally, thecontroller may determine the operational state based on data that may beinput by a user of the system. Furthermore, the operational state may bedetermined based on the status of the system and/or environmentalconditions.

In some embodiments, a controller may switch the operational state inresponse to detecting a parasitic device (using methods describedherein) that may be diverting power from a legitimate receiver. In anexample, a system may be operating in a state that utilizes common moderesonant coupling. However, a controller may detect a parasitic devicethat may also be coupled to the transmitter using common mode. Inresponse, the controller may stop wireless power delivery via the commonmode, and may enable wireless power delivery via a differentialcapacitive coupling mode, an inductive resonant coupling mode, or both.In other embodiments, a controller may use environmental conditions todetermine the system's operational state. For example, a controller mayreceive information indicative of a presence of high ferrite contentobjects in the system's environment. Accordingly, the controller maydetermine to operate in a mode that does not utilize inductive resonantcoupling mode.

A controller may also determine an amount of electrical power that asystem may deliver to each load in the system. The controller may alsomake a determination of how much electrical power to deliver to eachload via each available coupling mode in the system. Accordingly, in anexample, the controller may cause the power source to direct thedetermined amount of power to a resonator bank and further control thedelivery of power to the respective receivers via the respectivedetermined coupling modes.

Furthermore, external elements may be installed in a system'senvironment, which may be configured to improve or otherwise modify theperformance of the system. In some embodiments, field concentrators maybe configured to shape an oscillating magnetic field (of an inductiveresonator), an oscillating electric field (of a capacitive resonator),or both. For example, high permeability materials, such as ferrites, maybe installed in a system's environment. In an example embodiment, whilethe system is operating in inductive resonant coupling mode, the highpermeability material may be arranged so as to shape the oscillatingmagnetic field and extend its range. Similarly, high permittivitydielectric materials may be arranged in a system's environment. Acapacitor of the system may utilize the high permittivity dielectricmaterials to increase or otherwise modify its capacitance, and henceadjust the properties of the electric field produced by a resonantcapacitor. Furthermore, conductors may also be arranged in a system'senvironment so as to affect the magnetic and/or the electric fieldproduced by the system's resonators.

Within examples, a system may include circuit elements that may be usedas necessary in the system to implement the system's functionality. Forexample, a system may include circuit elements such as inverters,varactors, amplifiers, transmission lines, resonant cavities rectifiers,transistors, switches, relays, capacitors, inductors, diodes, andconductors. A relay may be used for switching between circuit elementsconfigured to operate each coupling mode. As explained herein, a switchmay connect a load to a receiver, such that the load is switchablycoupled to the receive-resonator. Other examples of possible uses forvarious circuit elements are possible.

B. Power Transfer to Legitimate Receiver(s)

FIG. 10 illustrates a resonant wireless power delivery system 1000according to an example embodiment. The system 1000 includes a powersource 1010, a transmitter 1020, and a receiver 1040. The transmitter1020 receives power from the power source 1010 and wirelessly transfersthis power to the receiver 1040. The transmitter 1020 may be one of aplurality of transmitters. The receiver 1040 is one of a plurality ofreceivers that may receive power from the transmitter 1020.

The transmitter 1020 includes a transmit-resonator 1022, and thereceiver 1040 includes a receive-resonator 1042. The transmit-resonator1022 is supplied with a power signal from the power source 1010oscillating at a resonant frequency ω₀. As described above, thetransmit-resonator 1022 resonates at the resonant frequency ω₀ andgenerates a field that oscillates at the resonant frequency ω₀. Thereceiver-resonator 1042 is correspondingly configured to resonate at theresonant frequency ω₀. The receiver 1040 is placed in sufficientproximity to the transmitter 1020 to couple the receive-resonator 1042with the field generated by the transmit-resonator 1022, e.g., thereceiver-resonator 1042 is within the field of the transmit-resonator1022 depending for instance on the quality factor Q as described above.This coupling establishes a resonant power transfer link 1002 thatprovides a wireless conduit for power transfer between thetransmit-resonator 1022 and the receive-resonator 1042. As alsodescribed above, the transmit-resonator 1022 and the receive-resonator1042 may be coupled via an oscillating magnetic field and/or anoscillating electric field. In particular, the coupling may include anyone or more of the following three modes: (i) inductive mode, (ii)differential capacitive mode, and (iii) common capacitive mode.

While the receive-resonator 1042 resonates in response to theoscillating field, a rectifier 1048 or other power conversion circuitmay convert power from the receive-resonator 1042 and subsequentlydeliver the power to a load 1060. While the load 1060 is incorporatedinto the receiver 1040 as illustrated in FIG. 10, some embodiments mayinclude loads that are physically separate or otherwise apart from thereceiver 1040.

As shown in FIG. 10, the transmitter 1020 includes a controller 1024. Inan example embodiment, the controller 1024 may determine what couplingmode(s) to employ and may control various elements of the transmitter1020 so as to establish and/or maintain wireless resonant coupling linksaccording to the determined coupling mode(s). The controller 1024 mayalso determine the amount of power that is transferred via therespective coupling mode(s).

As also described above, higher efficiencies can be achieved byadjusting impedances (resistance and/or reactance) on the transmittingside and/or the receiving side, e.g., impedance matching. Accordingly,the transmitter 1020 may include an impedance matching network 1026coupled to the transmit-resonator 1022. Similarly, the receiver 1040 mayinclude an impedance matching network 1046 coupled to thereceive-resonator 1042.

In an example embodiment, a plurality of devices and objects may bepresent within a local environment of the transmitter 1020. In such ascenario, the example system 1000 may be configured to distinguishlegitimate receivers from illegitimate devices that are not intendedrecipients of power transfer. Without an ability to discriminate betweenpossible recipients of power transfer, illegitimate devices may act asparasitic loads that may receive power from the transmitter withoutpermission. Thus, prior to transferring power to the receiver 1040, thetransmitter 1020 may carry out an authentication process to authenticatethe receiver 1040. In an example embodiment, the authentication processmay be facilitated via a wireless side-channel communication link 1004.

The transmitter 1020 may include a wireless communication interface 1028and the receiver 1040 may include a corresponding wireless communicationinterface 1048. In such a scenario, the transmitter 1020 and thereceiver 1040 may establish a side-channel communication link 1004 via awireless communication technology. For instance, classic BLUETOOTH® orBLUETOOTH® LOW ENERGY (BLE) (2.4 to 2.485 GHz UHF) or WIFI™ (2.4 GHzUHF/5 GHz SHF) may be employed to provide secure communications betweenthe transmitter 1020 and the receiver 1040. Other wireless communicationprotocols are possible and contemplated. As shown in FIG. 10, theside-channel link 1004 communicatively couples the transmitter 1020 andthe receiver 1040 over a secondary channel that is separate from theresonant power transfer link 1002. In alternative embodiments, however,the transmitter 1020 and the receiver 1040 may employ the same channelto transfer power and communicate information as described herein, e.g.,by modulating aspects of the power transfer to communicate theinformation.

In an example embodiment the transmitter 1020 can communicate with thereceiver 1030 over the side-channel communication link 1004 to determinethat the receiver 1040 is authorized or otherwise permitted to receivepower. The receiver 1040 may be configured to provide any type ofinformation and/or acknowledgement required by the transmitter 1020 toauthenticate the receiver 1040. For instance, the receiver 1040 maytransmit an authentication code, a message, or a key to the transmitter1020. In such scenarios, a device without the ability to establishside-channel communications with the transmitter 1020 may not beidentified as a legitimate device.

The receiver 1040 may also include a controller 1044. As such, thecontrollers 1024, 1044 can conduct communications via the side-channellink 1004 and process the information exchanged between the transmitter1020 and the receiver 1040.

As described above, when power is transferred from the transmitter 1020to the receiver 1040, power may be reflected back to the transmitter1020 As FIG. 10 illustrates, the transmitter 1020 may include abi-directional RF coupler 1030 to measure the reflected power as alsodescribed above. Using measurements from the bi-directional RF coupler1030, an optimal efficiency for the power transfer link 1002 may beascertained, and the impedance(s) on the transmitting and/or receivingsides can be adjusted via the impedance matching networks 1026, 1046 soas to optimize or otherwise modify power delivery efficiency.

The impedance associated with the receiver 1040 may be determined basedon the reflected power detected by measurement devices in conjunctionwith the bi-directional RF coupler 1030. If a nominal impedance (e.g., adesigned impedance) of the receiver 1040 is known, a difference betweenthe nominal impedance and the calculated impedance based on themeasurement of reflected power may indicate a presence of one or moreparasitic loads. Such parasitic loads may include illegitimatereceivers. Using the side-channel communication link 1004 establishedbetween the transmitter 1020 and the receiver 1040, the receiver 1040may be operable to communicate its nominal impedance to the transmitter1020. Thus, the calculation of impedance using the bi-directional RFcoupler 1030 may enable the identification of parasitic loads as well asenable dynamic impedance matching as disclosed elsewhere herein. Theimpedance(s) of the transmitter 1020 and/or the receiver 1040 can beadjusted via the impedance matching networks 1026, 1046 to account forthe parasitic loads.

As described herein, the transmitter 1020 may be operable to identifythe existence of the legitimate receiver 1040 through authenticationcommunications via the side-channel communication link 1004.Additionally or alternatively, the transmitter 1020 may be operable todistinguish the legitimate receiver 1040 from other legitimate orillegitimate devices by other methods. In particular, the transmitter1020 may be operable to control the power transfer link 1002 and thecommunication over the side-channel communication link 1004 with thesame receiver 1040.

FIG. 11 illustrates an example method 1100 for confirming that the powertransfer link 1002 and the side-channel communication link 1004 areestablished with the same receiver 1040. In step 1102, the transmitter1020 and the receiver 1040 may establish wireless communications via theside-channel communication link 1004. In step 1104, the receiver 1040sends authentication information to the transmitter 1020 viaside-channel communication link 1004, and in step 1106, the transmitter1020 evaluates the authentication information to determine that thereceiver 1040 is permitted to receive power.

Having identified the existence of the legitimate receiver 1040 via theside-channel communication link 1004, the transmitter 1020 may attemptto determine that the corresponding power transfer link 1002 isoccurring with the same receiver 1040. Accordingly, in step 1108, thetransmitter 1020 attempts to send a predetermined amount of power to thereceiver 1040 via the power transfer link 1002. In step 1110, thetransmitter 1020 communicates with the receiver 1040 via theside-channel communication link 1004 to confirm that the receiver 1040received the power transmission from step 1108. For instance, thereceiver 1040 can detect and report the power received. If the receiver1040 fails to provide information confirming the power transmission fromthe transmitter 1020, the transmitter 1020 in step 1112 can re-attemptto establish the power transfer link 1002 with the receiver 1040. Witheach re-attempt, the transmitter 1020 can change the amount of powerand/or modulate an impedance in an attempt to account for any parasiticloads that may be interfering with the power transfer to the correctreceiver 1040. Additionally or alternatively, the transmitter 1020 canchange the coupling mode(s) for the power transfer link. Once the powertransfer link 1002 to the correct receiver 1040 is established, thetransmitter 1020 can further modulate impedance, if necessary, andcontinue to transfer power to the receiver 1040.

In view of the foregoing, the side-channel communication link 1004 maybe employed to identify and authenticate the receiver 1040 and toestablish and adjust aspects of the power transfer link 1002,particularly to account for parasitic loads. Specifically, theside-channel communication link 1004 and the power transfer link 1002may enable a variety of authentication protocols so as to provide securecommunications and power delivery. For example, the transmitter 1020 andreceiver 1040 may be operable to conduct a password authenticationprotocol (PAP), a challenge-handshake authentication protocol (CHAP),multi-factor authentication, or another type of cryptographic protocol.In general, however, the transmitter 1020 and the receiver 1040 mayemploy the side-channel communication link 1004 to exchange any type ofinformation to manage any aspect of the power transfer link 1002.

In an example embodiment, the system 1000 may help ensure theavailability of the side-channel communication link 1004 byintermittently or continuously transmitting a certain amount of powervia a predetermined wireless resonant coupling link configuration. Thistransmission 1006 can power the wireless communication interface 1048and allow it to remain active even if other aspects of the receiver 1040do not receive power. As such, the receiver 1040 may receive sufficientpower to establish initial communications with the transmitter 1020.Thereafter, the receiver 1040 may establish the power transfer link1002. For instance, the transmission 1006 may provide a low power, e.g.,approximately 1 W. In such a scenario, the power distribution efficiencyof the transmission 1006 is less of a concern at relatively low powers.

As described above, the controller 1024 may determine what coupling modeto employ in the example system 1000. The controller 1024 may selectcoupling mode(s) based on the identification of parasitic loads. Forinstance, the transmitter 1020 may deliver power to the receiver 1040via a common capacitive mode during a first time period. However,subsequent to the first time period, the controller 1024 may detect aparasitic device that may also be coupled to the transmitter 1020 viacommon capacitive mode. Consequently, the controller 1024 may cause thetransmitter 1020 and/or the receiver 1040 to a switch to differentialcapacitive mode and/or inductive mode.

As shown in FIG. 12, the transmitter 1020 may also employ time-divisionand/or frequency-division multiplexing for the power transfer links 1002a-d to a plurality of legitimate receivers 1040 a-d, respectively.Although FIG. 12 may illustrate four receivers, it is understood thatany number of receivers may receive power from a transmitter accordingto the present disclosure.

Multiplexing may allow the transmitter 1020 to control how power isdistributed to the receivers 1040 a-d. For example, with time-divisionmultiplexing, power transfer during a given time period may be assignedto one or more specified receivers. With frequency-divisionmultiplexing, power may be transferred to specified receivers viarespective frequencies. In such a scenario, the transmitter may beconfigured to transmit a plurality of the respective frequenciessimultaneously. Thus, as illustrated in FIG. 12, the power transferlinks 1002 a-d may occur at various designated time and/or frequencycombinations (t, f)₁, (t, f)₂, (t, f)₃, (t, f)₄, respectively.Accordingly, the use of multiplexing may promote coordinated deliveryand availability of power to the receivers 1040 a-d.

Although the transmitter 1020 may transfer power to one receiver via asingle power transfer link having a particular time and/or frequencycombination as shown in FIG. 12, the transmitter 1020 in alternativeembodiments may transfer power to one receiver via multiple powertransfer links having different time and/or frequency combinations. Suchan approach provides some redundancy in case the transmitter 1020 isunable to transfer power with one or more of the power transfer links,e.g., due to interference from illegitimate receiver(s). The transmitter1020 can fall back on the remaining power transfer links to transferpower to the receiver without interruption. In general, the transmitter1020 can establish and selectively use any number of power transferlinks with a single receiver, where the power transfer links usedifferent respective time and/or frequency combinations.

The transmitter 1020 and the receivers 1040 a-d may employ side-channelcommunication links 1004 a-d as described above to coordinate themultiplexed transfer of power. For instance, the transmitter 1020 cancommunicate what time slots and/or which frequencies will be employed totransfer power to the receivers 1040 a-d. In an example embodiment,wireless power delivery utilizing time and frequency multiplexing may bemore secure than other wireless power delivery methods at least becausethe multiplexing scheme employed by the transmitter 1020 is likely to beunknown to illegitimate devices.

Without multiplexing, illegitimate devices with impedances or loadprofiles similar to legitimate devices might receive power withoutpermission. In cases where power resources may be limited, unpermitteduse of such power resources might result in denial of power tolegitimate receivers. Thus, multiplexing may allow more efficient androbust power transfer from the transmitter to any number of legitimatereceivers even in the presence of illegitimate or parasitic receivers.

It is understood that the use of a side-channel link is not limited tothe examples above. In an alternative implementation, for instance, atransmitter and a plurality of receivers may be pre-programmed withinformation regarding the multiplexing scheme for power delivery to theplurality of receivers. Additionally or alternatively, the transmittermay be pre-programmed with information regarding the nominal impedancesfor the receivers. In some cases, the receivers may have the sameimpedance. A side-channel communication link can then be used tocommunicate information that is not pre-programmed into the transmitterand/or the receivers. For instance, if a wireless power delivery systemis pre-programmed with the multiplexing scheme as well as informationrelating to the nominal impedances for the receivers, a side-channelcommunication link can be used by a receiver to report the powerreceived it has received so that the existence of any parasitic loadscan be determined as described above.

C. Repeaters

In accordance with example embodiments, the system may include one ormore resonant repeaters (or simply repeaters) configured to spatiallyextend the near field region of the oscillating field. Doing so mayenlarge the region around the transmitter within which receivers may beplaced in order to resonantly couple to, and receive power from, theoscillating field, as described above. In one example, a resonantrepeater may include a repeat resonator configured to resonate at theresonant frequency ω₀ of the system (the system resonant frequency) whenpositioned in the transmitter near field. Driven by the resonatingrepeat resonator, the repeater may then repeat the transmitter nearfield, thereby extending the range of the near field. Such repeater maybe passive, in the sense that they may be powered only by the near fieldin which they are positioned.

In an embodiment, a resonant repeater may receive a power signal via awireless resonant coupling link that may have been established with thetransmitter or with another repeater. As explained above, the wirelessresonant coupling link may be established when the repeater couples witha first near field of the transmitter or of another repeater. Therepeater may then emit the signal via a second wireless coupling linkestablished with another repeater and/or a receiver. Further, the signalthat is emitted by the repeater has an associated near field, with whichanother repeater and/or a receiver may couple. In some embodiments, therepeater may emit a signal such that the near field associated with theemitted signal is farther away from the transmitter than the extent ofthe first near field.

In further accordance with example embodiments, a plurality of repeatersmay be configured in a chain-like configuration, such that eachsubsequent repeater in the chain resonantly repeats the near field of anearlier link in the resonant repeater chain. The plurality of repeatersmay also be configured in array-like configuration. In such scenarios,the transmitter near field may be continually extended beyond itsoriginal range. Within examples, a repeater may establish severalwireless coupling links with one or more receivers and/or with one ormore repeaters. In some embodiments, a repeater may transmit power toone or more repeaters and/or to one or more receivers via a singlewireless resonant coupling link.

Furthermore, each repeater may be configured to couple with a magneticnear field and/or an electric near field. Each repeater may also beconfigured to repeat a magnetic near field and/or an electric nearfield. A repeater may couple with, and may repeat, various field typesdepending at least on the operational state of the system. For example,each repeater may couple with a transmitter or another repeater using atleast one coupling mode, according to the operational state of thesystem. Accordingly, each repeater may include at least one of a commonmode resonator, a differential mode resonator, and an inductiveresonator. The one or more resonator types that may be included in arepeater may be collectively referred to as a repeat resonator.

While the transmitter near field can be extended using one or morerepeaters, there may, however, be physical limitations to how far thenear field may be extended by chaining repeaters. Specifically, the nearfield will decay to some degree from one repeater to the next, so thateach repeated field produced by a passive repeater may have slightlylower, or substantially lower, average energy density than that producedby an earlier passive link. Thus, an accumulated decay may eventuallyyield little or no power transfer.

In accordance with example embodiments, the physical limitation due todecay of the near field may be overcome by including additionalcapabilities in the repeaters. For example, each repeater may include animpedance matching circuit that may improve the power transferefficiency from one repeater to another. In other examples, a system maymitigate decay of the near field by using active repeaters, each ofwhich includes an independent (secondary) power source. As such, theactive repeaters can “inject” additional power into the repeated fields.In one example embodiment, all of the repeaters of the system are activerepeaters. In another example embodiment, only some of the repeaters areactive repeaters, while others may be passive repeaters.

Within examples, an active repeater may “inject” additional power intothe repeated fields by applying a signal gain to the power signal thatthe active repeater receives from the transmitter or another repeater.The repeater may then emit the signal to another repeater or a receiver.In some embodiments, a repeater may be configured to apply a predefinedgain to the received signal. In other examples, a controller of thesystem may determine the gain that each active repeater applies to thereceived signal. For example, a controller may direct the activerepeater to apply a gain that is equivalent to the propagation losses ofthe signal. Thus, a load may receive the signal that has the samemagnitude as the original signal provided by the primary power source.Furthermore, in such a scenario, the extent of each repeater near fieldmay be similar to the extent of the transmitter near field. In otherexamples, an active repeater may be configured to emit a signal that maybe larger in magnitude than the signal that was emitted by thetransmitter.

Another physical limitation, discussed below, may arise due toaccumulated phase delay across chained repeaters. Also as discussedbelow, compensation for the effects of phase accumulation may beachieved by introducing adjustable phase shifts in repeaters, inaccordance with example embodiments.

D. Metamaterials and Phase Shift Adjustment

Generally, a phase shift may occur between the near field that arepeater couples with and the near field that is repeated by therepeater. Specifically, the phase shift may occur due to a propagationdelay of the power signal as the signal is received and subsequentlyemitted by a repeater. Alternatively or additionally, the phase shiftmay occur, at least in part, due to propagation of the electromagneticwave in a medium (e.g., air) between the transmitter and the repeater.Accordingly, each repeated near field produced by a given repeater willbe shifted in oscillatory phase with respect to that produced by anearlier repeater. However, if the accumulated phase shift acrossrepeaters in a chain approaches one-quarter of the resonant wavelength,the transmitter and the chain of repeaters will appear to behave like aradiating antenna array, and thus radiate power as an electromagneticwave in a far-field region of the antenna array. Such radiative behaviormay result in overall power loss and inefficient power delivery.

Radiation loss due to cumulative phase delay across a chain or an arrayof repeaters may be suppressed or eliminated by including one or morephase adjustment elements in some or all of the repeaters. Specifically,a repeater having a phase adjustment element may adjust the phase of itsrepeated near field. By appropriate phase adjustment, the near field ofthe system may be extended without becoming a radiating antenna array.Phase adjustment may be provided in a repeater by lumped elements, suchas inductors and capacitors, or by use of metamaterials, or both.Additionally and/or alternatively, the phase may be adjusted bydistributed elements that may have capacitive and/or magneticproperties.

A repeater may include phase adjustment elements that may be configuredto adjust the phase of a magnetic and/or electric field. As explainedabove, a near field type may depend on the operational state of thesystem. For example, a system may operate using inductive resonantcoupling and/or capacitive resonant coupling. As such, the near fieldthat is produced by a transmitter, and which is then repeated by eachrepeater, may be a magnetic field (associated with inductive resonantcoupling) and/or an electric field (associated with capacitive resonantcoupling). Within examples, the phase adjustment elements included ineach repeater may include any circuit element operable to adjust theinduced magnetic near field and/or the induced electric near field thatis associated with each signal emitted by each repeater. For example,each repeater may include lumped or distributed reactive components(i.e. capacitors and inductors) arranged to adjust a phase of a receivedsignal before and/or while repeating the signal.

In some embodiments, the phase adjustment elements of a repeater may beoperable to shift the phase of a near field that the repeater may couplewith. The repeater may subsequently regenerate the phase shifted nearfield such that another repeater and/or a receiver may couple with thephase shifted near field. More specifically, the repeater may shift thephase of the near field with respect to a phase of the near field at therespective location of the repeater. Alternatively, the repeater mayshift the phase, of the near field that it couples with, with respect toa reference phase of the oscillating field generated by thetransmit-resonator of the transmitter.

In accordance with some embodiments, a repeater may include ametamaterial configured to couple with a near field, and to repeat thenear field with a finite phase shift. Generally, a metamaterial is amaterial that may have properties not found in nature, due to the factthat its properties depend on its structure rather than on thecomposition of its elements. As a non-limiting example, the metamaterialmay include a split-ring resonator. In some embodiments, a metamaterialmay be configured to have a negative permeability, μ, and a negativepermittivity, ϵ. Such metamaterials may have a negative index ofrefraction, and thus may be referred to as negative index metamaterials(NIM). The index of refraction of a material may be defined as the ratioof the speed of light to the phase velocity in a material.

Therefore, a field that is incident on or that couples with an NIM maybe refracted with a negative phase velocity. Accordingly, a NIM may beconfigured to adjust the phase of a field oscillating at a resonantfrequency to which it may couple. In some embodiments, all of therepeaters of a system may include a NIM with negative permeability andpermittivity at the resonant frequency. In other embodiments, some ofthe repeaters of a system may be NIM, while other repeaters may berepeaters that include lumped/distributed reactive components.

Within examples, NIM may be configured such that the material may beadjustable so as to controllably shift the phase of a field (magneticand/or electric) at least based on a given resonant frequency. Asexplained herein, a repeater may couple with fields oscillating within arange of different frequencies, as the resonant frequency of the systemmay be adjusted dynamically. Accordingly, the NIM repeater may betunable so as to couple with, and shift the phase of, fields oscillatingat different frequencies. In some embodiments, a NIM repeater may be anactive repeater, which may “inject” power into the repeated field withthe shifted phase.

Within examples, each repeater may be configured to adjust the phasesuch that the near field of the emitted signal (i.e. repeated field) isin phase (or nearly so) with the near field produced by the earlier linkin the array of repeaters. Accordingly, the phase of each repeated fieldmay be “locked” to the phase of the transmitter near field. In such ascenario, phase-locking may prevent the overall electrical length of therepeaters from approaching one-quarter of the resonant wavelength. Sucha configuration of repeaters may be referred to as a “phase locked”array of repeaters.

However, shifting the phase of fields in a system may increase theoverall reactive power in the system. The increase in the reactive powerin the system may result in an increase of power losses in the system.Accordingly, in some embodiments, each repeater may be configured toadjust the phase of each repeated field by a determined amount such thatthe reactive power is reduced, while keeping the overall electricallength of repeaters in an array shorter than one-quarter of the resonantwavelength. As such some repeaters need not be configured to shift thephase of their respective repeated field to avoid increasing the overallreactive power in the system. In some examples, the controller of asystem may adjust the phase shifting elements of one or more repeatersin order to adjust the reactive power in the system. This adjustment ofreactive power in a system may be viewed as similar or analogous to apower factor correction, which may occur in conventional powertransmission systems.

FIG. 13 is a conceptual illustration of a relationship between a chainof repeaters and the phases of the respectively repeated near field ateach repeater, according to an exemplary embodiment. By way of example,a transmitter and a chain of five repeaters (labeled Repeater 1-5) areshown. For purposes of illustration, one full wavelength 1300 of a nearfield transmitted by transmitter as the resonant frequency of the systemis shown. Also by way of example, the repeaters are placed at incrementsof 0.1 wavelength from the transmitter, so that the last repeater in thechain as at one quarter wavelength from the transmitter. Wave 1300 isnot representative of the amplitude of the transmitter field, as thetransmitter field decays with distance. Rather, wave 1300 is meant toillustrate a wavelength of the transmitter field oscillating at theresonant frequency of the system.

FIG. 13A illustrates a resonant transmitter near field, which isrepeated by the repeaters 1-5 for the example case that includes nophase adjustment at the repeaters. As illustrated in magnified image1302 of FIG. 13A, each repeated field adds to the aggregate near field,and as such, the line representing the wave gets thicker as eachrepeater repeats the field that it couples with. Furthermore, eachrepeated field is phase shifted with respect to the field that precedesit. Thus, the aggregate of the phase shifted fields, at the 5threpeater, approaches one quarter wavelength of the transmitter nearfield. Accordingly, and as explained above, the aggregate of thetransmitter field and each of the repeated fields of repeaters 1-5, maycause the transmitter and the chain of repeaters to behave like aradiating antenna. Thus power may be radiated as an electromagnetic waveinto a far-field region of the transmitter.

FIG. 13B illustrates a resonant transmitter near field, which isrepeated by the repeaters 1-5 for the example case that now includesphase adjustment at the repeaters. As illustrated in FIG. 13B, the phaseof each repeated field is phase shifted, by its respective repeater, tomatch the phase of the transmitter near field. This may be an example ofa “phase locked” array of repeaters described above. More significantly,and as illustrated in magnified image 1304 of FIG. 13B, the aggregate ofthe phase shifted fields does not combine into a quarter wavelength ofthe transmitter near field. Thus, the transmitter and repeaters 1-5 maynot behave like a radiating antenna. Accordingly, far field radiationmay be suppressed or eliminated.

Furthermore, both the passive and active repeaters may include sidechannel communication interfaces, described above, in order tocommunicate with other components of the system, such as thetransmitter, the receiver(s), and the repeaters. For example, an activerepeater may receive instructions from a controller of the system, whichmay be located in the transmitter, to “inject” a specific amount ofpower into its repeated field. In an example, the controller may makethe determination for an active repeater to inject power based oninformation received from a receiver at the end of a repeater chain thatincludes the active repeater.

Furthermore, an array of repeaters configured to control the phase of afield may behave as a sort of collective metamaterial. As explainedabove, a metamaterial is a material that may have properties that arenot found in nature. As the array of repeaters may control the phaseshift in a way that is different from the natural phase shift thatoccurs while repeating and/or propagating a field, the array ofrepeaters may be considered as a collective metamaterial. Such an arrayof repeaters may be described as a metamaterial configured to suppressfar field radiation by controlling the phase of the field with which themetamaterial couples.

Accordingly, a chain or an array of repeaters configured to control thephase of a near field may be modeled as a single metamaterialelement/unit. For example, the single metamaterial unit may couple witha transmitter near field at one end. On the other end, a receiver maycouple with the phase shifted near field that is repeated by the singlemetamaterial. The phase shift of the repeated field may be the aggregateof the phase shifts of the individual repeaters that make up themetamaterial. In another example, the metamaterial may be a“phase-locked” metamaterial, such that the phase of the near field thatit repeats is identical to, or nearly identical to, a phase of the nearfield of the transmitter.

FIG. 14 illustrates a flowchart showing a method 1400 that may adjustthe phase of a signal from a transmitter near field as it is repeated byone or more repeaters of a system, according to an exemplary embodiment.In some embodiments, method 1400 may be carried out by a controller of asystem.

As shown by block 1402, of FIG. 14, method 1400 may involve causing apower source coupled to a transmitter to provide a signal at anoscillation frequency. The oscillation frequency may be one of the oneor more resonant frequencies of the transmit-resonator of thetransmitter. As shown by block 1404, method 1400 further includescausing the transmitter, in response to the signal from the source, toemit a transmitter signal associated with a transmitter near fieldregion. Accordingly, as shown by block 1406, the method further includescausing at least one of the one or more repeaters to receive arespective first signal associated with a respective first near fieldregion. Furthermore, the method includes causing each of the one or morerepeaters to shift a phase of the respective first signal by a specifiedamount. The respective first near field region of each repeater may bethe transmitter near field, or may be a near field that had beenrepeated by a prior repeater.

The method 1400 may cause at least one of the one or more repeaters toemit a respective second signal associated with a second respective nearfield region, as shown by block 1410. An extent of the second respectivenear field region may be configured to be farther away from thetransmitter than the first respective near field. Block 1412 may includecausing at least one of one or more receivers to couple to at least oneof the at least one final repeater. Accordingly, a wireless resonantcoupling link may be established between the each of the one or morereceivers and at least one of the at least one final repeater. As such,block 1414 may include causing the transmitter to transmit electricalpower to each of the one or more loads via at least one of the one ormore repeaters and the at least one of the one or more receivers.

E. Dynamic Wireless Power Distribution System Probe

Resonant wireless power transfer can be viewed as power transmission viaone or more wireless transmission “paths” or “links.” In addition togenerating an oscillating field for wireless power transmission asdescribed herein, the transmitter may also emit a “probe” signal inorder to ascertain various properties of the wireless power transmission“paths” and entities that interact with the power transferred via thepaths (e.g., receivers, repeaters, etc.). Such a probe can be used as atool for dynamic diagnosis and analysis of electrical “circuit”properties of a wireless power distribution system.

Thus, in accordance with example embodiments, a transmitter may includea signal generator, or the like, configured to transmit one or moretypes of wireless signals in order to determine one or moreelectromagnetic properties of propagation paths in the region in whichwireless power transfer may occur, and to further help distinguishand/or disambiguate between legitimate receivers and possibleunauthorized devices and/or parasitic loads. More specifically, thesignal generator may generate test signals that span a broad frequencyrange to provide a frequency sweep, in a manner like that of a vectornetwork analyzer (VNA) frequency sweep. By analyzing phase and amplitudeinformation of transmitted signals and their reflections, thetransmitter may thus determine electrical properties of a reflectingentity, as well as of the transmission path between the transmitter andthe reflecting entity.

In further accordance with example embodiments, the transmitter mayinclude a test-signal receiver component configured to receive andmeasure reflections of transmitted test signals. A controller associatedwith the transmitter may then determine one or more electromagneticproperties of a reflecting entity by comparing the transmitted testsignals with their corresponding reflections. By analyzing reflectionsof transmitted test signals, electromagnetic properties of variouspropagation paths, including the presence of, and electrical distancesto, reflecting entities, and electromagnetic properties of thosereflecting entities, may be ascertained. In practice, electricaldistance can be measured in terms phase shift or delay of a reflectedsignal with respect to a transmitted (reference) signal. With thisinformation, power delivery to legitimate devices can be optimized, andillegitimate power consumption can be identified and suppressed.Measurements and analyses can be carried out continuously, periodically,or episodically.

Test signals can carry both amplitude and phase information. In furtheraccordance with example embodiments, both types of information can beanalyzed to determine properties of a reflecting entity and of thepropagation path between the transmitter and the reflecting entity. Inan example application, test signals may be generated as continuouswaves of one or more frequencies, such one or more continuous sinusoids.In particular, by varying the frequency of a sinusoid (or other form orcontinuous wave) with time, either continuously or in a stepwisefashion, a test signal can be generated that sweeps across frequencies.For a typical application, the frequency may be varied linearly withtime such that the frequency sweep resembles a ramp (or staircase) infrequency with time. Such a sweep can be repeated from time to time, forexample. The reflections of a sweep signal can be measured by thetest-signal receiver and analyzed in a manner similar to a frequencysweep carried out with vector network analyzer. For example, thereflected sweep signal may display frequency-dependent phase delayscorresponding to electrical distance to a reflecting entity, as wellphase delays resulting from frequency-dependent interactions with thereflecting entity

In an alternative example application, test signals can be time-pulsemodulated. With this arrangement, reflections may correspond toindividually reflected pulses. Again, reflected signals may be measuredby the test-signal receiver. Measurement of pulsed signals and theirreflections may be used for time-of-flight analyses and/or other rangingtechniques. Single frequency continuous wave test signals, frequencysweep test signals, and pulsed test signals are non-limiting examples ofthe types of test signals that can be used to probe electricalproperties of a wireless power transmission region of a transmitter

Electromagnetic properties determined by analysis of test signals andtheir reflections can include impedance and admittance, for example.Reflecting entities can include receivers (both legitimate andunauthorized), repeaters, parasitic loads, and other that can interactelectrically with an electric and/or magnetic field. In an exampleembodiment, an analysis of phase and amplitude information from testpulses and their respective reflections may be used to determineelectrical “locations” of sources of impedance. For example,frequency-dependent characteristics of reflections and measured phasedelays can be used to map out electrical properties along a propagationpath. This can be viewed as analogous to how a VNA may locate stubs,taps, or shorts along a transmission path. In the context of wirelesspower delivery via an oscillating field, test signals can provide a sortof virtual “circuit diagram” of entities as mapped out in the wirelesspower delivery region.

In accordance with example embodiments, the virtual circuit diagramprovided by a frequency sweep can be used in the virtual circuit modelof the system to enhance the accuracy of the model and to help identifylegitimate receivers. As an example, by virtue of detected reflections,repeaters may appear as “hops” along propagation paths. Phase delays canthen be used to ascertain locations of repeaters in terms of electricaldistances to discontinuities in path impedances, for example. In anexample embodiment, mapping the system with one or more frequency sweepscan be carried out as part of the system initialization and repeatedfrom time to time to update the map. The initial map can then be used toassociate circuit locations with respective receivers as they make theirpresence known (e.g., authenticating, requesting power, etc.).

In an example system, analysis of phase delay and amplitude from afrequency sweep can be used to measure the impedance and couplingconstant of a receiver. This information can also be input to a virtualcircuit model of the system to improve the accuracy of the deducedcoupling constant at the operational resonant frequency of powertransfer, and thereby further optimize power transfer.

In further accordance with example embodiments, a frequency sweep testsignal and its reflection from a receiver can be used to determine anumber of repeater hops to the receiver. This can in turn be used todistinguish between a legitimate receiver known to be a certain numberof receiver hops away from the transmitter and an otherwise apparentlysimilar unauthorized receiver determined to be a different number ofhops away. For example, if analysis of a frequency sweep indicates thepresence of more than one receiver having the same (or nearly the same)impedance, these receivers may still be disambiguated by the respectivenumber of repeater hops to each respective receiver, as also determinedfrom analysis of test signals and reflections. A receiver determined tobe at an unrecognized number of hops away can thus be considered anunauthorized receiver, in which case the transmitter may take actions toprevent power transfer, as described above.

In accordance with example embodiments, the controller of thetransmitter can carry out the analysis of transmitted and reflected testsignals, including continuous wave signals, frequency sweep signals, andtime-pulse modulated signals, among others. In particular, thecontroller can control a signal generator to cause a specified type oftest signal or signals. The controller can also control a test-signalreceiver configured to detect one or more reflections and correlate themwith corresponding transmitted test signals. The controller can alsoperform one or more analyses of the transmitted and reflected signals todetermine the various properties and results described above.

Within examples, the controller may use test signals described herein tooptimize or otherwise adjust wireless power transfer as elements areadded to or removed from the system. In some embodiments, a system mayincorporate portable and/or non-stationary repeaters to extend the rangeof a transmitter. For example, a portable repeater may be added into thesystem in order to increase the range of a transmitter in a specificdirection. After an authentication process described herein, thecontroller may probe the environment of the system using a frequencysweep or other form of test signal in order to determine one or moreelectromagnetic properties of the added propagation path.

Furthermore, as explained above, a repeater may include phase elements,which may be adjustable. After determining the properties of thepropagation path that may include the repeater, the controller mayaccordingly send instructions to the repeater that direct its operation.Within examples, the controller may adjust the phase adjusting elementsof the repeater. In other examples, if the repeater is an activerepeater, the controller may also determine the amount of power that therepeater may want to inject into its repeated field.

Operations relating to use test signals described above may beimplemented as a method by one or more processors of a transmitter. Inparticular, the transmitter can include a transmit-resonator that isconfigured to couple power from a power source into an oscillating fieldgenerated by the transmit-resonator resonating at a resonant frequency.As discussed above, the oscillating field can be an oscillating electricfield, an oscillating magnetic field, or both. An example method 1600 isillustrated in the form of a flowchart in FIG. 16.

At step 1602, a signal generator of the transmitter transmits one ormore electromagnetic test signals at one or more frequencies. Inaccordance with example embodiments, the transmitted test signals willcarry both phase and amplitude information.

At step 1604, a test-signal receiver of the transmitter receives areflection of any given one of the transmitted test signals from one ormore reflecting entities. By way of example, a reflecting entity couldbe a repeater or a receiver. Like the given transmitted test signal, thereflection will carry both phase and amplitude information.

At step 1606, a processor of the transmitter determines one or moreelectromagnetic properties of a reflecting entity based on an analysisthe given transmitted test signal and a corresponding reflection. Inparticular, phase and amplitude information of the given transmittedtest signal and its corresponding reflection can be analyzed in a systemof equations to determine such properties as impedance of the reflectingentity and/or characteristic impedance of a propagation path followed bythe given transmitted test signal and its reflection.

It should be understood that steps or blocks of method 1600 as describedherein are for purposes of example only. As such, those skilled in theart will appreciate that other arrangements and other elements (e.g.machines, interfaces, functions, orders, and groupings of functions,etc.) can be used instead, and some elements may be omitted altogetheraccording to the desired results. Further, many of the elements that aredescribed are functional entities that may be implemented as discrete ordistributed components or in conjunction with other components, in anysuitable combination and location.

F. Example Applications

The example wireless power delivery systems described herein may beoperable to provide power to the any number of devices, systems, and/orelements of an “Internet of Things.” The Internet of Things may includeany number or combination of devices in a variety of configurationsand/or arrangements. In particular, one or more transmitters andoptionally one or more repeaters may be spatially organized to provideresonant oscillating fields within a given region, zone, area, volume,or other spatial bound. Other devices acting as receivers may eachinclude receive-resonators so that they may be operably coupled to theseresonant oscillating fields when located within the spatial bound. Insuch a scenario, each device may operably receive power via the resonantoscillating fields and may provide the power to one or more loads.

An example implementation may provide a household wireless powerdelivery system. For example, appliances and other electrically-poweredhousehold devices may be configured to receive power from transmittersand repeaters located throughout the household.

In such a scenario, the wireless power delivery system may increase theconvenience of using electrically-powered devices. As an example, theuse of the devices need not be limited to locations in the householdnear where wired power is accessible (e.g., wall outlets). In addition,the household may be dynamically reconfigured because devices withdifferent functions can be easily relocated in the household spacewithout requiring new wired power connections.

In some embodiments, a greater number of electrically-powered devicesmay be powered in the household at least because delivery of wirelesspower need not depend on a fixed number of physical connections to walloutlets, power strips, or extension cords. Rather, the wireless powerdelivery system may be configured to provide power to a large number ofdevices (e.g. hundreds or thousands of devices, or more). Furthermore,the wireless power delivery system may be configured to more-easilyaccommodate upgrades. In contrast to adding wall outlets and installingelectrical conduit in the household, an upgrade to a wireless powerdelivery system may include an-over-the-air software update. In such ascenario, the software update may enable the wireless power deliverysystem to provide wireless power to a larger number of devices byimproved time-domain multiplexing. Other upgrade types, functions,and/or purposes are possible.

Wireless power delivery systems contemplated herein may provideincreased household automation without extensive wiring. For instance,the household wireless power delivery system may provide power to asystem of automated windows, window treatments, doors, and/or locks.Also, the household wireless power delivery system may be configured toaccommodate room thermostats and other environmental monitoring devicesin each room. Additionally, the household wireless power delivery systemmay be operable to extend to exterior areas. For example, wireless powerdelivery to exterior areas may include providing electrical power toautomated garden sprinklers, outdoor lighting, outdoor cameras, securitydevices, and/or motion, heat, or other sensors. Furthermore, thehousehold wireless power delivery system may allow controls (e.g.,control panels for automated devices) to be flexibly and/or moveablylocated conveniently throughout the household.

As described above, example wireless power delivery systems may beconfigured to detect and identify various receivers within a localproximity. For example, the household wireless power delivery system maybe configured to locate household items that are resonantly coupled toit. Furthermore, the ability to locate household items need not belimited to electrically-powered devices that receive power from thewireless power delivery system. Non-electrically-powered devices, suchas keys, tools, utensils, and clothing, may also be located if, forexample, such objects may include a characteristic tag that may beidentifiable by the wireless power delivery system. For instance, theobjects may incorporate an RFID tag, may have a characteristic RFimpedance, or may include a receive-resonator as described elsewhereherein. Other types of tags or location devices may be incorporated intoobjects so as to find them via the wireless power delivery system.

In contrast to battery-powered devices, the household wireless powerdelivery system may provide continuous power to a device without needfor a battery or another type of energy-storage device. For instance, arobotic vacuum cleaning device receiving wireless power may movecontinuously within the household space without need for replacement orrecharging of batteries.

In another example implementation, a hospital wireless power deliverysystem is contemplated. Electrically-powered medical devices may beconfigured to receive power from transmitters and/or repeaters locatedthroughout the hospital. The hospital wireless power delivery system mayprovide advantages that are similar to the household wireless powerdelivery system above. For instance, medical equipment and other devicescan be easily and conveniently moved within the hospital without needfor new wired power connections. Additionally, the wireless powerdelivery system may be employed to locate hospital items that arecoupled to the resonant oscillating fields of the wireless powerdelivery system. In particular, surgical items may include a tag with areceive-resonator and/or a characteristic impedance detectable by thewireless power delivery system. In such a scenario, locating surgicalitems may help ensure nothing is inadvertently left in a surgical sitebefore closing the body cavity.

Currently, the use of portable electronic devices, such as phones,computer tablets, computer laptops, and watches, may be limited by theextent of their rechargeable battery power or access to a fixed walloutlet. Furthermore, the recharging process often requires a powerconnector to be attached to, and detached from, the portable electronicdevices. Repeated use of the power connector may lead to wear and tearand cause damage to the portable electronic devices.

Some portable electronic devices may employ conventional wireless powerdelivery systems. As described above, however, the coupling factor k insuch conventional systems must be maintained at a sufficiently highlevel in order to establish efficient power transfer. In other words,the portable electronic devices must be to be located in close proximityto, and precisely positioned relative to, the transmitter. Inconventional wireless power delivery systems, the transmitter musttypically have access to a fixed wall outlet. As such, compared to wiredrecharging which also requires access to a fixed wall outlet,conventional wireless power delivery systems merely eliminate the needto physically attach a power connector to the portable electronic deviceand provide no additional positional freedom for the use of the portableelectronic devices.

Thus, in yet another example implementation, wireless power deliverysystems may be employed in common spaces, such as airports, cars,planes, trains, buses, etc., to conveniently allow portable electronicdevices to be recharged and/or powered wirelessly. The portableelectronic devices may include receive-resonators that can be coupled tothe wireless power delivery system. In some cases, the rechargingprocess may occur automatically without user action when a portableelectronic device enters one of these common spaces. That is, theportable electronic device may automatically couple to wireless powerdelivery systems in proximity to the device. In other cases, a portableelectronic device may need to be registered via a wireless power accountand/or may need to be authenticated prior to receiving power from thewireless power delivery system. In some scenarios, the wireless poweraccount may be a paid account that may be associated with a wirelesscommunication network that may provide cellular (e.g. voicecommunication) and/or data services for the portable electronic device.

In a further example implementation, aspects of the present disclosuremay be employed to wirelessly assemble modular computer components. Asshown in FIG. 15, a computer system 1500 includes a plurality of modularcomputer components, which may include a computer processing unit/mainlogic board (CPU/MLB) 1502 a, a graphics processing unit (GPU) 1502 b,one or more hard disks (HD) 1502 c, a secondary optical read/write (R/W)device 1502 d, and a wide area network (WAN) card 1502 e. In otherembodiments, the computer system 1500 may include other/additionalcomputer components.

The GPU 1502 b, the HD 1502 c, the R/W device 1502 d, and the networkcard 1502 e may be communicatively coupled to the CPU/MLB 1502 a. Byexchanging data and other signals with the computer components 1502 b-e,the CPU/MLB 1502 a can centrally control the computer components 1502b-e. To establish such communications, the components 1502 a-e mayinclude respective wireless communication interfaces 1504 a-e as shownin FIG. 15. For instance, the wireless communication interfaces 1504 a-emay establish radio frequency (RF) communications (e.g., 60 GHz RF)and/or optical freespace communications between the computer components1502 a-e.

The computer system 1500 also includes a wireless power delivery systemto provide the components 1502 a-e with power. In particular, one ormore transmitters 1510 (and optionally one or more repeaters) arespatially organized to provide resonant oscillating fields within adefined spatial bound 1501. The spatial bound 1501, for instance, maycorrespond to the interior space of a hard case for a computerdesktop/tower. Each transmitter 1510 may be coupled to a power source1520 and may include a transmit-resonator 1516 to generate the resonantoscillating fields. The computer components 1502 a-e may each include arespective receive-resonator 1506 a-e configured to be coupled to theresonant oscillating field(s). When located within the spatial bound1501, each computer component 1502 a-e can receive power via theresonant oscillating field(s) to perform its respective function. Insome embodiments, the transmitter(s) 1510 may be integrated with theCPU/MLB 1502 a to centralize control of the computer system 1500further.

By establishing wireless communications and receiving wireless power,the computer components 1502 a-e within the spatial bound 1501 canfunction together as a computer. Advantageously, the wirelessconfiguration of the computer system 1500 eliminates the need for acomplex system of hardwired connections, e.g., wiring harnesses, toconnect the computer components 1502 a-e. Additionally, the wirelessconfiguration facilitates installation and removal of the computercomponents 1502 a-e, e.g., from a computer hard case. As such, thecomputer components 1502 a-e can be easily maintained, repaired, and/orreplaced. The computer system 1500 can also be upgraded just by placingadditional computer components, such as additional hard disks 1502 c, inthe spatial bound 1501 without setting up any hardwired connections. Insome embodiments, the CPU/MLB 1502 a may detect the presence of newcomputer components via the wireless communications and thus incorporatethe new computer components in the operation of the computer system1500.

As described above, the wireless power delivery system may employside-channel communications to coordinate aspects of the power transfer.As such, each transmitter 1510 may also include a wireless communicationinterface 1514 to communicate with each of the computer components 1502a-e acting as receivers. In other words, the communication interfaces1504 a-e may also be employed to provide side-channel communicationswith the transmitter(s) 1510.

As the computer system 1500 demonstrates, a system of components can beassembled according to a modular approach by employing a wireless powerdelivery system as well as wireless communications. Thus, in yet anotherexample implementation, a computer data center may employ a system oftransmitters and repeaters to allow computer servers to be implementedas modular components. The servers can receive power as long as they arelocated within the computer data center. In addition, wirelesscommunications, e.g., freespace optical communications, may be employedto allow data exchange between the servers. The wireless power deliverysystem and the wireless communications allow the servers to be easilydeployed in the computer data center without setting up wired power andwired network connections. The servers can be easily maintained,repaired, and/or replaced. Additionally, the servers can be spatiallyorganized in the computer data center with greater freedom. Although thetransmitters may receive wired power, the servers are not limited tolocations where wired power and/or wired network connections areaccessible.

Because the computer data center uses less wired power and fewer wirednetwork connections, the physical design of the computer data center canplace greater emphasis on other design considerations or features. Forinstance, the physical design can provide more optimal thermalmanagement. Alternatively, the physical design may focus on loweringcosts for building or implementing the computer data center.

G. Mobile Power-Delivery Systems

Some devices may operate out of range of a fixed resonant wireless powersource. In some cases, it may be impractical or difficult to provide afixed transmitter in a location where receivers operate or need tooperate. Examples include field devices, such as mobiledelivery/transportation vehicles, remote communication equipment, andclusters of devices in remote locations where fixed power sources arenot available.

In accordance with example embodiments, a system for resonant wirelesspower delivery can include a mobile node or device that is a hybridtransmitter/receiver (TX/RX) configured to move, travel, or “commute” toremote receivers and deliver power wirelessly based on the techniquesdescribed herein. More specifically, a hybrid TX/RX device can include atransmitter component (TX) having functionality of a transmitter, areceiver (RX) component having functionality of a receiver, and a powerstore for storing power (e.g., a battery) for supply to receivers. Thepower store may also serve as a power supply for various functions ofthe hybrid TX/RX device including, but not limited to, mobility(commuting), communications, control, and processing. The TX/RX devicecan be configured in an autonomous unmanned vehicle operational totravel between one or more fixed transmitters and one or more specifiedlocations that may be host to one or more remote receivers. In thelocation of the one or more remote receivers, the TX component mayfunction to wirelessly transfer power from the power store to the one ormore remote receivers. In the location of the fixed transmitter, RXcomponent can be configured to receive power via wireless powertransfer, and to use the received power to at least partially replenish(e.g., refill and/or recharge) the power store.

In an example embodiment, the hybrid TX/RX device may include ahigh-density stored power source, such as liquid fuel or a fuel cell.This source may be separate from the replenishable power store. Ahigh-density stored power source can be used to power operations of thehybrid TX/RX device and/or to provide power for wireless electricalpower transfer to receivers.

An autonomous unmanned vehicle can take on a variety of forms and modesof mobility. Non-limiting examples include an unmanned aerial vehicle(UAV), an unmanned ground vehicle (UGV), and an unmanned marine vehicle(UMV). A non-limiting example of a UAV is a multi-copter configured foraerial flight between locations and hovering at individual locations. Anon-limiting example of a UGV is a robotic wheeled vehicle configuredfor driving between locations and “parking” at individual locations. Anon-limiting example of a UMV is a robotic surface boat configured fortraveling over the surface of a body of water (e.g., ocean, lake, river,etc.) between locations and floating on the surface at individuallocations. A UMV could also be a robotic submarine vehicle. In someexamples, the autonomous unmanned vehicle may not necessarily park orhover at a location, but rather just “drive by” the location, possiblyat a reduced speed compared to the speed of travel to or betweenlocations.

Further, an autonomous unmanned vehicle can be fully autonomous orsemi-autonomous. A fully autonomous vehicle may be configured foroperation without human assistance or intervention, except possibly forhuman actions in loading or installing instructions prior to operation,for example. A partially autonomous vehicle may be configured foroperation with some degree of human assistance or intervention, such asremote or local control of at least some of the vehicle's operations.Unless otherwise specified or apparent from context, the term“autonomous unmanned vehicle” shall be taken herein to refer to bothfully and partially autonomous unmanned vehicles.

In an example embodiment, an autonomous unmanned vehicle can be a UAV.Herein, the terms “unmanned aerial vehicle” and “UAV” refer to anyautonomous or semi-autonomous vehicle that is capable of performing somefunctions without a physically-present human pilot. Examples offlight-related functions may include, but are not limited to, sensingits environment or operating in the air without a need for input from anoperator, among others. The term “aerial vehicle” (manned or unmanned)used herein refers to a vehicle configured for flight, and, depending oncontext, applies either during flight or when the aerial vehicle is notflying. The term “airborne vehicle” (manned or unmanned) refers to avehicle (such as an aerial vehicle) that is flying (or during flight).

A UAV may be autonomous or semi-autonomous. For instance, some functionscould be controlled by a remote human operator, while other functionsare carried out autonomously. Further, a UAV may be configured to allowa remote operator to take over functions that can otherwise becontrolled autonomously by the UAV. Yet further, a given type offunction may be controlled remotely at one level of abstraction andperformed autonomously at another level of abstraction. For example, aremote operator could control high level navigation decisions for a UAV,such as by specifying that the UAV should travel from one location toanother (e.g., from 123 Main Street, Anytown, USA to 987 First Avenue,Anytown, USA), while the UAV's navigation system autonomously controlsmore fine-grained navigation decisions, such as the specific route totake between the two locations, specific flight controls to achieve theroute and avoid obstacles while navigating the route, and so on. Otherexamples are also possible.

A UAV can be of various forms. For example, a UAV may take the form of arotorcraft such as a helicopter or multicopter, a fixed-wing aircraft, ajet aircraft, a ducted fan aircraft, a lighter-than-air dirigible suchas a blimp or steerable balloon, a tail-sitter aircraft, a glideraircraft, and/or an ornithopter, among other possibilities. Further, theterms “drone,” “unmanned aerial vehicle system” (“UAVS”), or “unmannedaerial system” (“UAS”) may also be used to refer to a UAV.

FIG. 17 is a simplified illustration of a UAV, according to an exampleembodiment. In particular, FIG. 17 shows an example of a rotorcraft 1700that is commonly referred to as a multicopter. Multicopter 1700 may alsobe referred to as a quadcopter, as it includes four rotors 1710. Itshould be understood that example embodiments may involve rotorcraftwith more or less rotors than multicopter 1700. For example, ahelicopter typically has two rotors. Other examples with three or morerotors are possible as well. Herein, the term “multicopter” refers toany rotorcraft having more than two rotors, and the term “helicopter”refers to rotorcraft having two rotors (e.g., a main rotor and a tailrotor).

Referring to multicopter 1700 in greater detail, the four rotors 1710provide propulsion and maneuverability for the multicopter 1700. Morespecifically, each rotor 1710 includes blades that are attached to amotor 1720. Configured as such the rotors may allow the multicopter 1700to take off and land vertically, to maneuver in any direction, and/or tohover. Furthermore, the pitch of the blades may be adjusted as a groupand/or differentially, and may allow a multicopter 1700 to performthree-dimensional aerial maneuvers such as an upside-down hover, acontinuous tail-down “tic-toc,” loops, loops with pirouettes,stall-turns with pirouette, knife-edge, Immelmann, slapper, andtraveling flips, among others. When the pitch of all blades is adjustedto perform such aerial maneuvering, this may be referred to as adjustingthe “collective pitch” of the multicopter 1700. Blade-pitch adjustmentmay be particularly useful for rotorcraft with substantial inertia inthe rotors and/or drive train, but is not limited to such rotorcraft.

Additionally or alternatively, multicopter 1700 may propel and maneuveritself and adjust the rotation rate of the motors, collectively ordifferentially. This technique may be particularly useful for smallelectric rotorcraft with low inertia in the motors and/or rotor system,but is not limited to such rotorcraft.

Multicopter 1700 also includes a central enclosure 1730 with a hingedlid 1735. The central enclosure may contain, e.g., control electronicssuch as an inertial measurement unit (IMU) and/or an electronic speedcontroller, batteries, other sensors, and/or a payload, among otherpossibilities.

The illustrative multicopter 1700 also includes landing gear 1740 toassist with controlled take-offs and landings. In other embodiments,multicopters and other types of UAVs without landing gear are alsopossible.

In a further aspect, multicopter 1700 includes rotor protectors 1750.Such rotor protectors 1750 can serve multiple purposes, such asprotecting the rotors 1710 from damage if the multicopter 1700 straystoo close to an object, protecting the multicopter 1700 structure fromdamage, and protecting nearby objects from being damaged by the rotors1710. It should be understood that in other embodiments, multicoptersand other types of UAVs without rotor protectors are also possible.Further, rotor protectors of different shapes, sizes, and function arepossible, without departing from the scope of the invention.

A multicopter 1700 may control the direction and/or speed of itsmovement by controlling its pitch, roll, yaw, and/or altitude. To do so,multicopter 1700 may increase or decrease the speeds at which the rotors1710 spin. For example, by maintaining a constant speed of three rotors1710 and decreasing the speed of a fourth rotor, the multicopter 1700can roll right, roll left, pitch forward, or pitch backward, dependingupon which motor has its speed decreased. Specifically, the multicoptermay roll in the direction of the motor with the decreased speed. Asanother example, increasing or decreasing the speed of all rotors 1710simultaneously can result in the multicopter 1700 increasing ordecreasing its altitude, respectively. As yet another example,increasing or decreasing the speed of rotors 1710 that are turning inthe same direction can result in the multicopter 1700 performing ayaw-left or yaw-right movement. These are but a few examples of thedifferent types of movement that can be accomplished by independently orcollectively adjusting the RPM and/or the direction that rotors Y10 arespinning.

FIG. 18 is a simplified illustration of a UAV, according to an exampleembodiment. In particular, FIG. 18 shows an example of a tail-sitter UAV1800. In the illustrated example, the tail-sitter UAV 1800 has fixedwings 1802 to provide lift and allow the UAV to glide horizontally(e.g., along the x-axis, in a position that is approximatelyperpendicular to the position shown in FIG. 18). However, the fixedwings 1802 also allow the tail-sitter UAV 1800 take off and landvertically on its own.

For example, at a launch site, tail-sitter UAV 1800 may be positionedvertically (as shown) with fins 1804 and/or wings 1802 resting on theground and stabilizing the UAV in the vertical position. The tail-sitterUAV 1800 may then take off by operating propellers 1806 to generate theupward thrust (e.g., a thrust that is generally along the y-axis). Onceat a suitable altitude, the tail-sitter UAV 1800 may use its flaps 1808to reorient itself in a horizontal position, such that the fuselage 1810is closer to being aligned with the x-axis than the y-axis. Positionedhorizontally, the propellers 1806 may provide forward thrust so that thetail-sitter UAV 1800 can fly in a similar manner as a typical airplane.

Variations on the illustrated tail-sitter UAV 1800 are possible. Forinstance, tail-sitters UAVs with more or less propellers, or thatutilize a ducted fan or multiple ducted fans, are also possible.Further, different wing configurations with more wings (e.g., an“x-wing” configuration with four wings), with less wings, or even withno wings, are also possible. More generally, it should be understoodthat other types of tail-sitter UAVs and variations on the illustratedtail-sitter UAV 1800 are also possible.

As noted above, some embodiments may involve other types of UAVs, inaddition or in the alternative to multicopters. For instance, FIGS. 19Aand 19B are simplified illustrations of other types of UAVs, accordingto example embodiments.

In particular, FIG. 19A shows an example of a fixed-wing aircraft 1900,which may also be referred to as an airplane, an aeroplane, or simply aplane. A fixed-wing aircraft 1900, as the name implies, has stationarywings 1902 that generate lift based on the wing shape and the vehicle'sforward airspeed. This wing configuration is different from arotorcraft's configuration, which produces lift through rotating rotorsabout a fixed mast, and an ornithopter's configuration, which produceslift by flapping wings.

FIG. 19A depicts some common structures used in a fixed-wing aircraft1900. In particular, fixed-wing aircraft 1900 includes a fuselage 1904,two horizontal wings 1902 with an airfoil-shaped cross section toproduce an aerodynamic force, a vertical stabilizer 1906 (or fin) tostabilize the plane's yaw (turn left or right), a horizontal stabilizer1908 (also referred to as an elevator or tailplane) to stabilize pitch(tilt up or down), landing gear 1910, and a propulsion unit 1912, whichcan include a motor, shaft, and propeller.

FIG. 19B shows an example of an aircraft 1950 with a propeller in apusher configuration. The term “pusher” refers to the fact that thepropulsion unit 1958 is mounted at the back of the aircraft and “pushes”the vehicle forward, in contrast to the propulsion unit being mounted atthe front of the aircraft. Similar to the description provided for FIG.19A, FIG. 19B depicts common structures used in the pusher plane: afuselage 1952, two horizontal wings 1954, vertical stabilizers 1956, anda propulsion unit 1958, which can include a motor, shaft, and propeller.

UAVs can be launched in various ways, using various types of launchsystems (which may also be referred to as deployment systems). A verysimple way to launch a UAV is a hand launch. To perform a hand launch, auser holds a portion of the aircraft, preferably away from the spinningrotors, and throws the aircraft into the air while contemporaneouslythrottling the propulsion unit to generate lift.

Rather than using a hand launch procedure in which the person launchingthe vehicle is exposed to risk from the quickly spinning propellers, astationary or mobile launch station can be utilized. For instance, alaunch system can include supports, angled and inclined rails, and abackstop. The aircraft begins the launch system stationary on the angledand inclined rails and launches by sufficiently increasing the speed ofthe propeller to generate forward airspeed along the incline of thelaunch system. By the end of the angled and inclined rails, the aircraftcan have sufficient airspeed to generate lift. As another example, alaunch system may include a rail gun or cannon, either of which maylaunch a UAV by thrusting the UAV into flight. A launch system of thistype may launch a UAV quickly and/or may launch a UAV far towards theUAV's destination. Other types of launch systems may also be utilized.

In some cases, there may be no separate launch system for a UAV, as aUAV may be configured to launch itself. For example, a “tail sitter” UAVtypically has fixed wings to provide lift and allow the UAV to glide,but also is configured to take off and land vertically on its own. Otherexamples of self-launching UAVs are also possible.

In accordance with example embodiments, a mobile TX/RX device may travelto a location of a receiver that is otherwise out or range of any otherfixed transmitter. At the location, the mobile TX/RX device may thenposition itself sufficiently close to the receiver so that the receivercan couple to an oscillating field produced by the TX component of themobile TX/RX device. The mobile device may determine an appropriatedistance of approach according to its resonant wavelength, for example.It may also determine the distance to the receiver using a rangedetector, such as a laser. Additionally or alternatively, it may use atest-signal generator in a mode that transmits a test pulse, asdescribed above, and measure a round-trip delay based on a reflectionfrom the receiver. Once the mobile TX/RX device determines it issufficiently close to the receiver, it may begin wirelessly transferringpower from its power store (e.g., a battery) to the receiver accordingthe techniques described above.

In an example embodiment, the mobile TX/RX device may travel to alocation of a transmitter. At the location, the mobile TX/RX device maythen position itself sufficiently close to the transmitter so that itsRX component can couple an oscillating field of the transmitter. Themobile device may determine the distance to the transmitter using arange detector, such as a laser. Additionally or alternatively, it mayuse a test-signal generator in a mode that transmits a test pulse, asdescribed above, and measure a round-trip delay based on a reflectionfrom the transmitter. Once the mobile TX/RX device determines is itsufficiently close to the transmitter, it may request wireless poweraccording the techniques described above. It may use the receivedwireless power to power its own operations (e.g., flying or driving)and/or to replenish its power store (e.g., recharging a battery) forsubsequent delivery of wireless power to one or more remote receivers.

In an example embodiment, the mobile TX/RX device may include afar-field receiver configured for receiving power from a far-fieldbeaming transmitter. Non-exclusive examples of a far-field beamingtransmitter include a microwave transmitter and a laser transmitter. Ineither example, power may be wirelessly transmitted to the far-fieldreceiver at a level sufficient to replenish the power store. Far-fieldbeaming of power may be used when a line-of-sight path between thefar-field transmitter and the far-field receiver is available.

Operations relating to mobile TX/RX device described above may beimplemented as a method by one or more processors of the mobile TX/RXdevice. In particular, the mobile TX/RX device, more generally referredto as a mobile wireless power-delivery device (MWPD), can include anautonomous mobile vehicle, a power source, and a transmitter deviceincluding a transmit-resonator that is configured to couple power fromthe power source into a first oscillating field generated by thetransmit-resonator resonating at a first resonant frequency. The MWPDcan also include a receiver device including a receive-resonatorconfigured to resonate at a second resonant frequency in response tobeing situated in a second oscillating field generated by a power-supplytransmitter other than the transmitter device of the MWPD. Further, inresponse to the receive-resonator resonating at the second resonantfrequency, the receiver device may transfer at least a portion of powerof the second oscillating field to a rechargeable component of the powersource. The first and second oscillating fields can each be anoscillating electric field, an oscillating magnetic field, or both. Anexample method is illustrated in the form of a flowchart in FIG. 20.

At step 2002, a controller of the MWPD causes the autonomous vehicle tomove to a first location in sufficient proximity to a remote receiver tocause the remote receiver to couple with the first oscillating field.Step 2004 includes the controller causing the autonomous vehicle totransfer power to the remote receiver via the first oscillating field.

At step 2006, the controller of the MWPD causes the autonomous vehicleto move to a second location in sufficient proximity to the power-supplytransmitter to cause the receiver device to couple with the secondoscillating field. Step 2008 includes causing the autonomous vehicle toreceive power from the power-supply transmitter via the secondoscillating field.

It should be understood that method 2000 is described herein forpurposes of example only. As such, those skilled in the art willappreciate that other arrangements and other elements (e.g. machines,interfaces, functions, orders, and groupings of functions, etc.) can beused instead, and some elements may be omitted altogether according tothe desired results. Further, many of the elements that are describedare functional entities that may be implemented as discrete ordistributed components or in conjunction with other components, in anysuitable combination and location.

FIG. 21 depicts a simplified block diagram of a MWPD 2100 in accordancewith an example embodiment. As shown, the MWPD 2100 includes arepresentative autonomous vehicle 2102, which in practice may constitutea physical platform for some or all of the other components of the MWPD2100. The MWPD 2100 also includes a power source 2104, a transmitter2106, and a receiver 2108. By way of example, the components aredepicted as being connected by a bus 2112, which could supportcommunication between components, as well as power supply and/or otheroperational aspects of the MWPD 2100. Although not shown in FIG. 2100,the MWPD 2100 could include a payload for carrying out other tasks.

By way of example, FIG. 2100 also includes a representative remotereceiver 2114, including a receiver load, and a representative fixedtransmitter 2116, including its own power supply. Example operation,such as described above and discussed in connection with FIG. 20, isillustrated conceptually by the motion arrow 2117 representing travel ofthe MWPD 2100 between the fixed transmitter 2116 and the remote receiver2114. While at the location of the fixed transmitter 2116, the receiver2108 of the MWPD 2100 may receive power wirelessly via an oscillatingfield 2115 generated by the fixed transmitter 2116. The received powermay be used to power operations of the MWPD 2100 and possibly torecharge or replenish the power source 2104 of the MWPD 2100. While atthe location of the remote receiver 2114, the MWPD may deliver powerwirelessly to the remote receiver via an oscillating filed 2113generated by the transmitter 2106 of the MWPD 2100. It will beappreciated that the simplified block diagram of FIG. 21 and thesimplified example operation description are intend for illustrativepurposes.

III. Conclusion

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for providedfor explanatory purposes and are not intended to be limiting, with thetrue scope being indicated by the following claims.

The invention claimed is:
 1. A method carried out by a mobile wirelesspower-delivery device (MWPD), wherein the MWPD comprises an autonomousmobile vehicle and a controller communicatively coupled to theautonomous mobile vehicle and configured to carry out operationsincluding causing the autonomous mobile vehicle to move the MWPD tospecified geographic locations, the method comprising: (a) causing theMWPD to (i) move, by navigation of the autonomous mobile vehicle, to afirst location in sufficient proximity to a remote receiver to cause theremote receiver to couple with a first oscillating field generated by atransmit-resonator of a transmitter of the MWPD resonating at a firstresonant frequency, wherein the first oscillating field is at least oneof an oscillating electric field or an oscillating magnetic field, and(ii) transfer power to the remote receiver via the first oscillatingfield, wherein the transmit-resonator is configured to couple power froma rechargeable power source of the MWPD into the first oscillatingfield; and (b) causing the MWPD to (i) move, by navigation of theautonomous mobile vehicle, to a second location in sufficient proximityto a power-supply transmitter, other than the transmitter of the MWPD,to cause a receive-resonator of a receiver of the MWPD to couple with asecond oscillating field generated by the power-supply transmitter,wherein the second oscillating field is at least one of an oscillatingelectric field or an oscillating magnetic field, and (ii) receive powerfrom the power-supply transmitter via the second oscillating field,wherein the receive-resonator is configured to resonate at a secondresonant frequency in response to coupling to the second oscillatingfield, and wherein the receiver is configured to, in response to thereceive-resonator resonating at the second resonant frequency, transferat least a portion of power of the second oscillating field to therechargeable component of the power source.
 2. The method of claim 1,wherein the autonomous mobile vehicle is one of an unmanned aerialvehicle (UAV) configured for moving by flying, an unmanned terrestrialvehicle (UTV) configured for moving by traveling on solid ground, or anunmanned marine vehicle (UMV) configured for moving by traveling on orunder water.
 3. The method of claim 1, further comprising: the MWPDtransmitting one or more electromagnetic test signals; the MWPDreceiving a reflection of any given transmitted test signal reflected byone or more reflecting entities remote from the MWPD; and determiningone or more electromagnetic properties of a reflecting entity of the oneor more reflecting entities based on at least a corresponding reflectionfrom the reflecting entity.
 4. The method of claim 3, wherein the methodfurther comprises determining a distance to the reflecting entity bydetermining a round-trip propagation delay of a transmitted test signaland a corresponding reflection from the reflecting entity, wherein thereflecting entity is one of the remote receiver or the power-supplytransmitter.
 5. The method of claim 3, wherein each test signal has anamplitude and phase, and the corresponding reflection has an amplitudeand phase, and wherein determining the one or more electromagneticproperties of the reflecting entities comprises comparing the amplitudeand phase of at least one transmitted test signal with the amplitude andphase of the corresponding reflection.
 6. The method of claim 1, whereinthe first location is a first path that passes in sufficient proximityto the remote receiver to cause the remote receiver to couple with thefirst oscillating field, and wherein transferring power from the powersource to the remote receiver via the first oscillating field while theMWPD is at the first location comprises transferring power from thepower source to the remote receiver via the first oscillating fieldwhile the MWPD is in motion on the first path.
 7. The method of claim 1,wherein the second location is a second path that passes in sufficientproximity to the power-supply transmitter to cause the receive-resonatorof the receiver of the MWPD to resonate at the second resonantfrequency, and wherein receiving power from the power-supply transmittervia the second oscillating field while the MWPD is at the secondlocation comprises receiving power from the power-supply transmitter viathe second oscillating field while the MWPD is in motion on the secondpath.
 8. The method of claim 1, further comprising: authenticating theremote receiver via a communication interface of the MWPD prior totransferring more than an initial amount of power to the remote receivervia the first oscillating field.
 9. The method of claim 1, furthercomprising: authenticating with the power-supply transmitter via acommunication interface of the MWPD prior to receiving more than aninitial amount of power from the power-supply transmitter via the secondoscillating field.
 10. A non-transitory computer-readable medium havinginstructions stored thereon that, when executed by one or moreprocessors of a mobile wireless power-delivery device (MWPD) comprisingan autonomous mobile vehicle configured to move to specified geographiclocations, cause the one or more processors to carry out operationsincluding: (a) causing the MWPD to (i) move, by navigation of theautonomous mobile vehicle, to a first location in sufficient proximityto a remote receiver to cause the remote receiver to couple with a firstoscillating field generated by a transmit-resonator of a transmitter ofthe MWPD resonating at a first resonant frequency, wherein the firstoscillating field is at least one of an oscillating electric field or anoscillating magnetic field, and (ii) transfer power to the remotereceiver via the first oscillating field, wherein the transmit-resonatoris configured to couple power from a rechargeable power source of theMWPD into the first oscillating field; and (b) causing the MWPD to (i)move, by navigation of the autonomous mobile vehicle, to a secondlocation in sufficient proximity to a power-supply transmitter, otherthan the transmitter of the MWPD, to cause a receive-resonator of areceiver of the MWPD to couple with a second oscillating field generatedby the power-supply transmitter, wherein the second oscillating field isat least one of an oscillating electric field or an oscillating magneticfield, and (ii) receive power from the power-supply transmitter via thesecond oscillating field, wherein the receive-resonator is configured toresonate at a second resonant frequency in response to coupling to thesecond oscillating field, and wherein the receiver is configured to, inresponse to the receive-resonator resonating at the second resonantfrequency, transfer at least a portion of power of the secondoscillating field to the rechargeable component of the power source. 11.The non-transitory computer-readable medium of claim 10, wherein theautonomous mobile vehicle is one of an unmanned aerial vehicle (UAV)configured for moving by flying, an unmanned terrestrial vehicle (UTV)configured for moving by traveling on solid ground, or an unmannedmarine vehicle (UMV) configured for moving by traveling on or underwater.
 12. The non-transitory computer-readable medium of claim 10,wherein the operations further include: causing a signal generator ofthe MWPD to transmit one or more electromagnetic test signals; causing atest-signal receiver of the MWPD to receive a reflection of any giventransmitted test signals reflected by one or more reflecting entitiesremote from the MWPD; and determining one or more electromagneticproperties of a reflecting entity of the one or more reflecting entitiesbased on at least a corresponding reflection from the reflecting entity.13. The non-transitory computer-readable medium of claim 12, wherein theoperations further include determining an electrical distance to thereflecting entity by determining a round-trip propagation delay of atransmitted test signal and a corresponding reflection from thereflecting entity, wherein the reflecting entity is one of the remotereceiver or the power-supply transmitter.
 14. The non-transitorycomputer-readable medium of claim 12, wherein each test signal has anamplitude and phase, and the corresponding reflection has an amplitudeand phase, and wherein determining the one or more electromagneticproperties of the reflecting entities comprises comparing the amplitudeand phase of at least one transmitted test signal with the amplitude andphase of the corresponding reflection.
 15. The non-transitorycomputer-readable medium of claim 10, wherein the first location is afirst path that passes in sufficient proximity to the remote receiver tocause the remote receiver to couple with the first oscillating field,and wherein transferring power from the power source to the remotereceiver via the first oscillating field while the MWPD is at the firstlocation comprises transferring power from the power source to theremote receiver via the first oscillating field while the MWPD is inmotion on the first path.
 16. The non-transitory computer-readablemedium of claim 10, wherein the second location is a second path thatpasses in sufficient proximity to the power-supply transmitter to causethe receive-resonator of the receiver of the MWPD to resonate at thesecond resonant frequency, and wherein causing the receive-resonator toreceive power from the power-supply transmitter via the secondoscillating field while the MWPD is at the second location comprisescausing the receive-resonator to receive power from the power-supplytransmitter via the second oscillating field while the MWPD is in motionon the second path.
 17. The non-transitory computer-readable medium ofclaim 10, wherein the operations further include: authenticating theremote receiver via a communication interface of the MWPD prior totransferring more than an initial amount of power to the remote receivervia the first oscillating field.
 18. The non-transitorycomputer-readable medium of claim 10, wherein the operations furtherinclude: authenticating with the power-supply transmitter via acommunication interface of the MWPD prior to receiving more than aninitial amount of power from the power-supply transmitter via the secondoscillating field.